I guess the big issue here is hes not using a big "tank"... a tank usually is considered a fish "tank" with glass on the sides and the bottom... Hes got wood on all sides but the front. Wood is a much better insulator than glass and holds the humidity/heat much better... With solid wood on all sides the stress is limited bc the snakes cant see past the wood... in a glass tank the snake can see everything and may feel more vulnerable bc of this... I think the OP should try get his temps/humid. where they need to be and try it out... If it works it works... If not you set up a smaller tub and go from there... It takes like 10 mins to set up a tub so its not like its that big of a deal.

Connie pointed out many options to try and make it work... try it out and see what happens... the snakes not going to die or something in a couple days... Let em settle in offer food and see what happens.