You might want to figure out how much you're likely to use the harness for DP. Usually the dildo mounts over the penis, so if you like the missionary position that means that your penis will penetrate her anus. If you go doggie style than your penis will be in her vagina, and woman-on-top depends on which way around she is.

The reason you'll want to look at the likely use is because harnesses designed for men are fewer in number and more expensive - the Ulti-Mate is probably the most affordable example.

The next tier down are harnesses that will work for male use even if they are not specifically designed for it. Most of the jock style harnesses fit this camp, except possibly the low-riders (Jaguar and Outlaw Leather models).

Then there are the ones that don't work - most G-string harnesses and the ones with big blocking pieces like the SpareParts.

Answering the question from the other post:

It's pretty much guaranteed that the dildo will mount over the penis. The rationale is fairly simple - above the penis you have the pubic bone (a great place to have the base of the dildo rest), while underneath the penis there isn't much space, and what space is there is taken up by the scrotum and testicles.