The PoCo in my area allows 2" GRC up to 3' high to be unguyed. I have seen a few masts, 2" GRC, that have been stuck up in the air 8' (eight) with a single guy wire off to the structure.
As for the hole, quite a while back I picked up an extra deep hole saw (2-1/2" deep) sized for 2" GRC that came with a 2-1/2' shaft. The shaft on this unit has a 2-1/4' closed end pipe mounted to it by sealed ball bearings; this allows the shaft to turn independent of the pipe. The pipe is just a titch smaller than the cut of the hole saw.
I set up under the eave, put the hole saw pilot bit on my mark, position the pipe on the shaft parallel to the wall, eyeball the pipe on the shaft vertical from side to side, and then I run the whole thing right up through the soffit and out the shingles. The pipe on the shaft keeps the hole saw centered as the hole saw pilot bit starts into the underside of the roof sheathing.
Al
