We're looking to sink our standalone spa about 20" into the ground so that it doesn't block the view from the master bedroom windows. We don't have a lower spot in the yard to assist with the drainage so we know we'll need to have the PB do a sump pump inside the spa box with a covered hatch/area to the control panel. It's a Bullfrog spa and they do have their own spa vault but we've got a couple of bids from PBs that wanted to create the box out of fire block and one that would shoot it with gunite. anyone had something similar done? any issues with how it was done? anything to avoid, etc..?