If you can manage it, the ideal scenario is two (or more) beams on the same
tower, with switching and phasing that allows you to run them in phase, out
of phase, or separately. That gives you the flexibility of both a high tower
and a low one, and the ability to refine the gain at the arrival angle of
the signals you're interested in. Having a telescoping tower that you can
move to different operating heights provides another level of flexibility.
Regarding HFTA, while I think it's a wonderful tool, be aware that the
arrival angles it uses are based on VOACAP, which means they are averages
only. There will be (many) times when those numbers don't apply -- which is
another reason some flexibility is ideal.
As far as optimizing the choice of pointing direction for a dipole from
mid-Texas, you might have a look at my ViewProp app. It has a feature that
shows antenna coverage fans on a map; you can use a slider to move the fans
around and optimize coverage for the areas you're most interested in. More
info at http://zl2ham.wikispaces.com/ A quick look based on a rough QTH
shows two promising alternatives: around 142 deg heading would give you JA
in one direction and the Caribbean and South America in the other; while
about 214 deg would give you Europe in one direction, and XE and ZL in the
other.
73, Rick ZL2HAM (ZM1G/ZL1G)
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