I am not sure there is such a dichotomy as you imply between "being nice" and "being an a**hole".
In the circles I used to move in (negotiating major weapons contracts for the U.S. Navy), the contracts ran to hundreds of pages--and that's incorporating most of the clauses by reference, and similarly with the specifications and such of the items to be delivered. But the reality was, your word was your bond: if you couldn't be counted on to make good, the whole system would grind to a halt as the lawyers took over (this is what happened back in the 1990s with the Navy stealth fighter/bomber, the A-12): lots of money would get wasted and we still wouldn't get a proper product.
So my sense is, you need to establish two things: first, that you're a standup guy (or gal, in your case), and that you will do whatever it takes to fulfill your commitments (this would be the "nice" part), and second, that if the other fella screws you, you will take him down by whatever means necessary (that would be the "a**hole" part).
I don't really take being a standup guy as "nice" incidentally: for me, it's all about honor, and personal and professional integrity. Dunno if that works for you.
Anyhow, always enjoy your blog! :-)