Wanted to come up with an easy way to seal the holes through the van floor that are needed for the sink drain, power wiring, propane pipe, and other services. The solution was to get some 1/8" thick x 2"wide x 36' long aluminum from Home Depot. Then drill some holes in it and cut it to length. Cut some butyl rubber sheet to match the aluminum with holes sized for the the pipe or wire passing through it.
Here is the cut aluminum and butyl rubber sheets. A leather punch was used to punch the holes for the screws and wire. A mat knife was used for larger holes.
To make life easier the mounting holes were drilled from the top inside the van.
Butyl rubber caulk was placed between the aluminum and the butyl rubber sheet and again between the rubber sheet and the van body. Then the the assembly was screwed to the van body. Additional caulk was placed in some areas.
From the inside the van the caulk was smoothed to seal the raw edge of the large hole.
Now just need to wait for the caulk to set before installing the pipe and wire.