RE: 90kg and 7.5...what size board?
With 90kg rider iS111, the uphaul with 7.5m is possible but challenging. It's certainly possible in "emergency" situations, but maybe not something that a normal rider would like to do a lot (unless they like that challenge - some do !).
With 122 you have a marginal improvement in early planing threshold - and maybe a more significant edge in light slalom conditions (once planing) as the 122 holds very strong planing power from early on in the range (when 111 can be planing but not fully efficent). Note here that in "marginal 111 " conditions, especially with heavier riders, the 122 will have the best top speed/range.
In ultimate top end speed, by the time the 111 is really flying, the most likely winner in the "outright" top speed" is the 111; the 122 can challenge but by the conditions the 111 is reaching top speed (in normal water) the water become a little rough and the 122 remains very fast BUT 122 definitely becomes more demanding (skill/determination/resiliance) to ride at very top speed in rougher chop.
Hope this clarifies the discusion, please let us know if more info is required.
Cheers ~ Ian