A while back, I'd gone through the effort of fabbing up some brackets so I could sling a Viair 2.5 gallon tank under the slider-door sill area.
However, not long after that project, I realized how heavy my rig had gotten, so I started questioning all my life choices. Eventually, I bagged that project and embarked on a more holistic pursuit of putting the van on a diet. I have, however, followed through on mounting a compressor. My justification is that I'd be carrying a portable compressor anyway, so this was a worthwhile trade-off for a supreme convenience.
I have been using a Viair 400p since our first American Adventurist Desert Rendezvous in 2012, and found it to be more than adequate for my ~30" tires. A few years ago, I scored a good deal on a used 400c (the fixed-mount version) at another American Adventurist gear swap, and I figured a one-to-one exchange would work out well.