Sounds plenty big enough to me, for housing (separately) a corn & a house snake. Keep in mind that corns appreciate height, with branches to climb in.

Wood cabinets are tricky to convert to safe snake housing, since most furniture finishes are toxic, & obviously you know that moisture is an issue too, so you need to
seal all the wood with a "no-voc" waterproofing ("voc" - volatile organic compounds...in other words, once dry, it must be aired out completely & not continue to off-
gas "organic compounds" (which are not healthy for us OR pets to breathe). Exact product names escape me for the moment, I haven't converted any furniture for
many years now, but others here have (so either search some DIY threads or wait for others to chime in, or ask around, & google search).

Wood is a great insulator, and both the snakes you mention don't need such high heat as boas & BPs do, but you still need to make safe choices. I do NOT suggest
using UTH, since the heat has trouble penetrating the wood "floor" and is more likely to over-heat the UTH by trying to. I also think that RHP's would be over-kill, &
while some ppl install heat lights (for the warmth) or CHEs (that's like a light for warmth only it's heat only, no light) in wood enclosures, you'd then need welded wire
"cages" around them (so the snakes cannot contact them) & they still aren't the safest option (because sometimes snakes splash water, or climb & the wire is abrasive.

What I'd personally do is use either a small flat ceramic "uth" (if you can find one? I have some stored from years ago, but I'm not sure anyone sells them now?) that
is controlled by thermostat, OR buy a short heat cable (they are used outside to prevent pipes from freezing, so they aren't sold for pets, only in home improvement-
hardware stores) & do the same thing - regulate it w/ thermostat. Either of the last 2 suggestions have a normal power cord: I'd drill a small hole in the wood back,
just big enough for the cord itself to pass thru. I'd snip off the plug (you don't want to make a hole that big, you'll only have to seal it up), & replace the plug once I
installed it. They sell easy-to-install replacement plugs in hardware stores too.

A heat cable can be wound around a branch, or installed along the bottom side of an enclosure...use your imagination. The important thing is to properly regulate it
with a thermostat. Heat cables & ceramic UTH are both designed to be used outdoors (the ceramic UTH I have were designed to be used in zoos, under the dirt floor
of animal exhibits). This is UNLIKE the typical heat tape aka "UTH" (of any brand, Flexwatt "style"- like that sold by Reptile Basics & others), as those are NOT safe
to put inside enclosures, they're designed only for underneath glass etc. where no moisture can contact them.

I agree, it's extremely bad form to burn your house down, & your pets would greatly prefer you don't do that also... Safety first!