[TowerTalk] Taller tower, shorter mast or vice versa?

[Alan AB2OS]

The township rules permit an antenna/tower/mast up to a max. of 70' 
without a permit. I have settled on AN Wireless as my preferred tower 
manufacturer, and their towers are in multiples of 10'. Thus a 60' tower 
with a mast extending the remaining 10' gives me only 10' within which 
to mount all my antennas -- or less, since I wouldn't want an antenna 
immediately at the top of the tower. All I intend to put up at first is 
a 3-el. SteppIR (which I *might* perhaps upgrade to a 4-el. later), and 
perhaps a 2m/70cm beam, so for now that 10' mast is sufficient, but who 
knows what I might decide to put up later?

Would it be preferable to get the 50' tower and a mast extending a 
further 20'? The mast would obviously have to be something rather 
substantial (chrome moly?), so there would be little cost saving over 
the taller tower and the shorter mast.

Have other people wrestled with this question, and what decision was 
reached?

Note: AN Wireless' surface area/wind loading specs already allow for the 
antennas being mounted up to 10' above the top of the tower. If I went 
with 20' of mast, I'd mount the SteppIR at about the 10' level and the 
smaller antenna(s) above that.

Alan AB2OS