Roger will likely jump in, but here is my take. Any of the futuras from the 122 up will help you plane a little bit earlier, carry throught the lulls better and will be comfortable to slog.
However, the gain in early planing will be minimal if you stay with the 7.5 as your largest sail. To receive the benefit of a larger board, you should invest in larger sails. Your 7.5 is ideal for your carve 111, but you should be looking at an 8.5 and possibly a 9.5 if you jump up to a futura 133 or the 141. One of these two boards would be my recommendation to go with your 111. I would look at the 141 first to better cover the light wind days.
Larger sails will call for larger booms and masts, so the costs can go up significantly. On the other hand, if you sail often, you will not doubt gain a lot from a larger sail. If you only sail occasionally, I wouldn't give up on larger sails, but I would look at the used sail / mast / boom market to find something bigger at a low cost. I would do this too even if you go for the 141.
If you are worried about managing bigger sails, I weigh 170 lbs and have a 7.6, 8.4, 9.2 and 11.0 sails, plus all the smaller ones. However, I do sail a formula board, which really needs the large sails to perform. My next board down from the F160 is an iSonic 111.
All of this depends on the typical conditions in which you will sail. Give us a little more information regarding your experience, how much you sail and in what contitions, and we (Roger) can refine the answer.
Hope this helps.