I assume, as Gary stated, this is a carrier in the receiver on the back of the camper. There are several factors in play A RECEIVER may be rated at 350 lb, but the way it was installed may not support the load. Likewise, we have seen cases where vehicle was rated for 350 lb max hitch load but it had a 500 lb max load receiver. The max ix still 350 lb - weakest link. A good welder can inspect it and correct any deficiencies if needed.
If it is truly good for 350 lb, that extra 5 lb does not matter!