I needed to do the same in my Voltage garage, and called Dutchmen.
The customer service rep that I spoke with told me that, except for the generator & auxiliary fuel tanks, which are thin and located to the very rear of the rig... there are no other tanks under the garage area flooring.
Basically he said that I could drill holes in the floor anywhere within the "front 4 feet" of where my garage meets the interior living area of the rig, and not hit anything.
So I did... I drilled 2 pilot holes for my Condor chock mounting plate, and simply used large lag bolts to secure it into the floor. Have used it twice with my big ole Gold Wing, and it's held everything secure.
2013 VOLTAGE 3200 (EPIC I & II)
2014 Ford F-450 PLATINUM