[TowerTalk] Bracketed but Unguyed Monopole

[WT4BT-Barclay Thomas]

My aim: Vertical support for a Hexbeam at about 30-35 feet.
Space for guys is severely limited by property lines, trees and other structures
I cannot use a lattice type tower for several reasons.
Ground here is clay over ledge/bedrock and only 18 - 24 inches deep so anchors may be marginal without rock drilling.
I am in a 70 mph wind zone (90 mph @ 30 sec. gust zone) here on the Cumberland Plateau in So. Central TN.

What I am thinking of:
Mast system like the Penninger Radio “Tipper” 35 foot using 2” x 0.25” (rather than the stock 0.125") wall tubing (8’,10’ or 12’ sections) which would be bracketed to the shack building (separate from the main house) at about the 10-12 foot level.

Yaesu G-450, or similar, rotator at top of mast turning a Hexbeam with maybe a 6 meter short-boom yagi (3-5 elements).
There would be 1 or 2 pulleys below the rotator for inverted V or L antennas and “experimental wires” as the mood strikes.

Base of mast would be in concrete (TC-24 concrete base mount) but the amount poured might be sub-optimal (can go somewhat wide but not deep).

As noted above, guying will be a compromise situation.

Due to roof overhang on main house bracketing to it, or trying to mount a shorter mast off the face of a dormer is not a strong option. Roof mount a la Glenn Martin is possible but the roof pitch is greater than 12 in 12 so getting up there to do any work is not an option for me.
 
Questions:
Can I get away with the top 25 or so feet of mast being unsupported (unguyed)?
Are there any other suggestions or thoughts for doing what I want?
Different mast or tubing suppliers?

Mac / WT4BT