You need to note that my comments are mainly personal opinions and thoughts which are based to what I have seen and experienced. Maybe there is carbon layer is somewhere and I just haven seen it. Edea´s soles are made leather type synthetic material. Under this layer there is plastic "insole". If you dont drill screw holes all the way to the sole, fat tip HI-LO screws stops to this harder layer under the synthetic leather and screw starts to pull out the softer material. If you just continue tightening the screw, soon you have over sized hole. This same is valid for most of the Risport shoes.
In both brands heels mounting is secured with quite big screws from insole side. Edeas soles as hollowed, kind of honeycombed when Risport soles are made from leather layers, which means that are solid. Honeycomb design save weight, but they increase also risk to break drill in to the hole. It has happened several times to me that my drill has hit also to screw, nail or side of the honeycomb wall inside the Edea heel. They all will break easily 2.5 mm thick drill.
Ones the drill went broken in one of the slotted holes. Broken drill bit was so deep in the heel that I didn't have any changes to pull it out. I was wondering what to do now. I decided to try if that piece of drill what I cannot pull out could work as a nail. I took some nail or similar pin what I used to hammer drill so deep to heel that I can use Edeas screw to push it even deep in to the heel. I though that everything went well when screw was tightening normally and blade mounting was secured. When I everything was ready with that boot, I removed that skate from my blade mounting stand I realized that that drill bit was now inside the honey comb heel and was causing terrible rattling noise. OMG...what do now I thought. They were Edea Ice Fly, so not the cheapest Edea boots and fault was mine. I was thinking that I have three chaises.
1. Buy new boots for this skater and say that I will never-ever mount blades to anyone else boots that mine own.
2. Inject glue trough the screw hole and hope that glue drops in to the piece of drill and holds it on place until boots are replaced with new ones.
3. Drill enough big hole in to the middle of heel and try some magnet fishing or some other method to get that drill bit out from that hole. The problem is that I do not have X-ray eyes so I didn't know if I can get that drill out even I would drill larger hole in to the middle of heel. It could be possible that my hole would be if different cell than where the piece of drill is.
Option 1 was so expensive that I decided that I will try first all other options. Option 2 sounded also a bit risky in long term. What about if my gluing works just some days or couple months? So I ended up to option 3 and finally everything went well. In that moment I was really considering if mounting blades to other people is wort of all those risks. So those whom are paying skate techs from blade mountings, keep in your mind what kind of risks skate techs are taking. Risk has to included in their prices. Imagine how many blades you need to mount if you fail in 500$ boots.
What comes to plugging unused holes to prevent moisture entering to empty screw holes / sole, I would claim that it is important only in boots with leather soles. Personally I really dont like leather soles as leather and moisture is never good combination. Due this they have to be protected with lacquer layer or Snow-Seal and glue has to be used in the screw holes even you would use screw in that hole. Leather is like a sponge which is sucking all water what it just can hold. Synthetic material does not have this issue and this the reason why I like Edea boots.
If "empty" holes would be serious issue in Edea boots, why Edea is making empty holes already at the factory. If you try to google pictures from the Edea boots, You can see that intersection area between the sole and heel has several holes. Often insole has also holes as well as plastic sole under the insole. I have even seen pictures where Edea demonstrates how "steam" comes out from these holes. At lest my understanding is that they are made for air ventilation purposes. Nevertheless I have not plugged holes in Edea boots if that has not been necessary to secure blade mounting. I have to confess that I am lacy to fill holes if I see it unnecessary. I know that many persons here in Europe whom are filling the holes in Edea boots simply with epox. When synthetic sole will not damage from the moisture, cant we see that glue makes perfect copy from the HI-LO screw which has formed "threads" to the sole? You just need to find correct glue type. Perhaps two component plastic metal could work if viscosity is correct.
Recently Edea has started to apply some friction mat between the insole and brown plastic "insole". Sometimes there has been problems that their insoles start to slip. Attached one example picture from the skates which were given to me for sharpening. Later that sent me message that if I could check what is the wrong in one boot when they daughter complains that she can feel some lump inside the boot and it hurts. It was quite obvious what was the reason.
Some tips to the Edea boots...
* If boot has only size marking on the sole (example 245, ), its last width is C. If it is something else like B, D or E, they will mark it next to the size marking.
* Boots are far from the planar and way too often there is huge cap between the blade and sole
* Check always the backstay seams. In some reason seams in left foot might be tilted quite a lot.