I will pipe in because I was pretty worried about this too. I went from the stock deluxe wheel set up to a 15" wheel and truck tires 29" tall. You can feel a difference but it is not too bad at all, less than I thought. I downloaded an app on my phone and did some runs 0-60mph in 95 degree weather and it was about a 1.5 sec difference. In stock form I was about 18 sec and with the new rims and tires I was 19.4 sec. I know the app is not great but it was free, now for the fun stuff. My stock wheel with 700+ miles (half worn) weighed 35lbs for the fronts and 46lbs for the rears so a total of 162ish pounds, and the new setup is 54lbs each for a total of 216lbs, a difference of over 50lbs!
I know you can get the Power Command with auto tune and that should help the low end, but I have not gotten it yet. The only real loss I can tell is the 58mph and up seems to be slower. I don't normally travel that fast so it does not bother be at.
Let us know if you find a different tuner that works..