I think very carefully before entering spaces like that these days.. (And I have entered many since I started in 1995).... One time, I suited-up (Tyvek 100%, the face mask, gloves, the whole show) and entered a similarly-constricted crawl space through a standard 1950's vintage rectangular cellar window... I'm inside and proceed to systematically probe the sills/joist-ends and rim joist areas (the rims were insulated) and BANG... right into a freakin' bee's nest that 'blew up' with bees.. I skedaddled my keister out that window at super-high speed and ended up bruising the **** out of my hips in the process.. Morale of story: When entering extremely constricted space, ask yourself, "Can I get out of here relatively fast or not and safely". Often it's the 'fast exit' that cannot be accomplished well.. The Tyvek kept the bees away thankfully... but the injury on the hips lasted for a week..