I'm curious which places have a 24' length limit? If these are off road, back country NFS or BLM sites with narrow, winding, unpaved roads in/out, the length limit is probably to keep you from getting stuck, or damaging your vehicle or the flora.
Cruise America made up a list of more mainstream NPS park limits... it looks close (except Big Bend NP which will handle longer RVs).
https://www.cruiseamerica.com/rv-adventures/rv-lifestyle/national-park-rv-size-limit Generally speaking, a 26 footer won't find many places that can't handle it.
