[TowerTalk] tower base question

[Bill K2OWR]

My entire property seems to contain a serious rock shelf about 3' down everywhere I dig.
I would like to dig a hole down to that rock surface, then drill and install some rebar or something before I pour concrete in order to anchor to the rock at least a little.

I plan to gin pole the tower up as I have done several times in the past., 
I don't think I need the sort of base I put in for free standing crankups , since this one will be seriously guyed 3 ways at 3 points
So mostly the base is for support from sinking. My plan is to attach/weld some rebar to one section, then sink it into the hole and fill with concrete.
Since I can only get three feet down I was thinking maybe I could drill and epoxy some rebar into that rock and just pour around the tower section I put in there.

Does this make sense?
If not, what do you recommend?
If it does, do I just drill holes and lay in the rebar? What do I use for epoxy?

BILL K2OWR