hmmmm so i got my magnets but im having a bit of trouble with them. im cant find a great spot where the bio touches the mask properly, therefore the bio wont stay put.... how many magnets are you guys using? i got the 20mm magnets and they are well strong so i thought 2 would hold a bio but obviously not.... does anyone have any tips?
You could try building up a couple of areas inside the bio so it makes closer contact with the mask. This could easily be done with milliput epoxy putty. That would also acts as anchors points for the magnets. Pretty sure it would work and you haven't compromised the bio as the additions are on the inside and not visible.
I put quite a lot of them in mine (9 or 10), because I wanted to have it stick even if the mask shifted as it was put on and made some closer to the bio and some not.
Regarding filling the distance between the bio and the mask:
I put about 3/8" thick foam in the bio, then a leather layer to which I epoxied the magnets.
Then a thin leather liner went over that to hide the leather, magnets, and glue.