Plano area huaa?? I'm in Ft Worth. I have 2 different rafts, both are set up very different because of the size and use. If you are going to have "paddle assist" while you are rowing, I would set the oar towers toward one stearn so the passengers have plenty of room to paddle w/ out hitting the oars or them just being in the way. If you will just be rowing w/ no assist, then set it up how you are comfortable. Everybody is a bit different. After spending a little time rowing it, you will quickly work out any kinks in the system. So, determing where exactly your seat is in relation to the towers depends on your leg length. If your legs are long, you'll be hitting you knees w/ the oars.
Good luck, let's hope for more rain!