my fave is you lay on your side, legs make a L shape (so the top leg goes up in the air) he is on his knees right up so his thighs are on either sides of your bottom leg. He can hold that leg youve got up in the air for balance or for your comfort. bellies or big bottoms dont get in the way at all, works for all sizes.

hands and knees, rear entry... i cuddle a ton of pillows(helps the belly) and DH on his knees holding my hips.(and not leaning on me at all)

never have enough energy to do the chair one during preggy, more exercise than pleasure.. but that could just be me..