2.5' in upper mish is a good minimum level for a fun, less scrapy run down, but it starts to get really fun around 3.5' to 4' and up. the waves are big and pushy at that level, and there is a lot more play to be had. never done upper rustic so can't say for sure. this warmer weather coming in over the next few days should kick the flows up for your visit.
if you need a boating partner when you get closer to your visit, i'll show you the river from upper mish on down.
By the waterside I will lay my head.
Listen to the river sing sweet songs to rock my soul.