Of the four shot sizes commonly used for upland shooting, those being #6, #7, #7.5, and #8 I wonder why even consider #7.5 shot?
The shot sizes on either side of 7.5 are superior to 7.5. With #8 shot you get a denser pattern and with #7 shot you get larger and heavier shot, both being far superior to 7.5 on both accounts.
In answer to your question Tom, I use RST #7 a lot of the time for grouse and woodcock, often using #8 in the right barrel and #7 in the left earlier in the season and later when the foliage is down and birds often flush farther out I might use #7 in both barrels for the energy carrying capacity of the larger shot.
YMMV
