yes you can run PVC conduit under the frame.
if you are not mounting the inverter next to the batteries: Keep in mind that first you must determine the conduit route, the length of wire from the batteries to the inverter, then the wire size adjusting for voltage drop. then you can size the conduit to the wires.
If you can mount the inverter near the batteries and just want a outlet for the rv to plug into, then its easier. You can run 1/2" PVC conduit under the frame to you desired location. run say #12 wire to a RV plug. then just plug the power cord for the RV into that.
My setup as an example: The batteries are on the A frame up front. converter/power panel mid ship, the inverter just behind that. Solar comes down to the compartment with the inverter. I ran 1.5 inch PVC conduit from the batteries to the compartment with the converter. ran #4 wire to there, and into the inverter compartment. I then ran #14 SJO cable from the inverter to a RV outlet to the compartment where the shore power cord is located. The end at the inverter has a regular plug on it and is plugged into the inverter. What I do is unplug the shore power cord from the outlet at my home before I head off to destinations unknown. I plug it into the RV outlet I mounted inside the shore power cord compartment. When I need 120v ac, I just turn on the inverter.
There are some things I have to mention...1 I keep the converter breaker off at all times. When using the inverter, you must as well. Solar maintains my batteries. 2 I don't use the microwave or the air conditioner. 3 the fridge and hot water heater are on propane only.
2000 Cherokee 29BH with 6V batteries, LED lights & 400 watts of solar power, flipped axles and raised. 2007 Tundra 5.7L DC-LB with lots of mods. C-co, 8/158th AVN Maint.