"Harry K" wrote in message
news:1583afa4-82f9-4b4b-ad0b-

stuff snipped

Excellent points. The worry about 'crackign the block' is no biggee.
The likely hood of making a tight fitting 2" hole without using a core
drill is zero so it will have to be patched in any case. I have done
the BFH route and patched the remains later, used a 3/8" hammer drill
and small concrete bit and probably a few other methods. If I ever
have to do it again it will be 'rent a real electric hammer and decent
bit, drill a ring of holes and knock out with hammer' Of course being
careful to miss the web.

It's beginning to look like renting the right gear is the way to go.
Thanks!

--
Bobby G.