For the Solera I think the 350lbs is a bit of a stretch given that the hitch is pretty far behind the rear wheels and thus creating a huge lever to the front wheels by adding weight.
I wouldn't fill the water tank until the last minute (it is stored far to the rear as well) and then move all heavy items as far forward as you can. The nice storage under the bed should only contain light items.
Bike (with hitch) will be around 300lbs and you need to add that weight again to the front to balance your setup better. Apart of that you would need stiffer springs in the rear.
There's a lot of replies here about trailers - this is a Motor home carrying a bike on the rear trailer hitch....