The 35s with slps will still give good bottom end, especially if you are running higher compression with race fuel numbers. But I ran 35s with race fuel and the mpg was not ideal, I ran a pingel and ran outta gas in the trails a handful of times. I switched to stock carbs and pump gas and I tell ya, it was way more practical for the type of riding you are going to be doing. Id stick the the smaller carbs because the bottom end was much more responsive with the smaller carbs, you will be happy with the 28s and still be able to smoke most average joes play dragging. As far as jetting, with my 35s and race fuel (170+ psi) I was at 52 pilot, 138 main (small i know) dont start this low if you go this route, and cel needle in the 3rd or 4th position dont remember. Stock carbs was 37.5 pilot, 350-370 main, vitos needle in the middle or 4th.
edit: I now run their 7 mil setup with 35mm carbs. not much more to $build$ minus the more expensive supporting mods. gas mileage same story