I'm dealing with the same issue as the RV cinch-type seat belts are not really good for car seats.
I'll be picking up a new View in a few weeks and I'm already planning to replace the cinch belts with a retractable, locking belt which is more secure for a car seat base. You can get those a Summit Racing.
Still looking for a good source of a tether anchor which will add even more security.
Tom and Katharine
'07 Winnebago Tour 40TD, 400hp Cummins
'17 Winnebago View 24V, '02 R-Vision B+
RVing for 20 years & 200,000+ miles