Fireman It did not weaken it at all, but if care is not taken when doing it, it most certainly can. Initially I was going too deep, but after a couple I realised it and did not go as deep.
It does not take long at all for the dimple to be made, so a couple seconds of the iron on the plastic is all that is needed...
Geist, those grips work great... I just get tired tired of having to buy little things all the time.. It is like the spending never stops. I had been making grips like the one you listed out of Bicycle Inner tubes and tape... I would roll the tape and then place where I wanted it, then put the inner tube over it.. And it would form grooves like you have on that pic for the fingers..