A generator of 2900w will run somewhere around 80-90lb...let's call it 120 with a couple 5 gal jugs of gas.
2 additional deep cycle batteries can weigh that much...in reality, you need a lot more than 4 batteries to take advantage of even 2000w of solar. On an RV, you probably have to go lithium at significant additional cost to keep the weight under control.
Speaking of weight, how much cargo capacity do you have left...that's a lot of stuff being added.
As someone else mentioned, on the side, you will be over width.
Biggest difference is generator is on demand power. You start it up any time, you have the power. Solar puts out power for a short period mid-day. Morning and evening, power output is a small percentage of the rating. Night, shady site or overcast, you don't get much of anything.
This isn't to suggest solar is bad but you have to understand it's limits and make sure it can really do what you are thinking it can do.