You’re good with a Pedaltrain Classic - they’re raised at the back with room to mount the power supplies underneath. I’ve got a Truetone CS12 mounted under mine.
I’ve had two Pedaltrain boards - a Classic and a Metro, they’ve both been perfect. Sturdy, not too heavy, robust soft bags.
You'll have no problem. Depending on the type of power supply you probably just need to get a pair of mounting kits, which are irritatingly pricey compared to the good value for the pedalboard itself. Or just velcro the things straight to the underside if you think heat won't be a problem.
Ta loves. Last question, will mounting two small 5 output powers supplies be an issue on a pedaltrain classic?
Edit: fuck it i'll deal with that later. Just ordered a Pedal Train 2 off a shop in Bournemouth via Reverb for £99.