They're hinged on one side, so they always seem to go up with the canvas on the left. I reckon they're the best looking poptop personally, you get the proper shape of the roof, and they look cool 'popped' with the sky lights. They didn't only do panelvans by the way, they did kombis like most companies. Also, i'd swap slightly worse aerodynamics for the ability to stand up straight any day
Don't cut the hole until you've done your homework. Dormobile roofs are HEAVY. You need some meaty well fixed steelwork with the right bracketry for the sprung-loaded supports. Grinder is fine but watch out for the sparks ruining the glass.
Listen to Zed, he knows what he's talking about. Also, treat the spring loaded support arms with RESPECT - a friend of mine nearly caused himself serious injury when one of them whacked into his arm.
zed i do have the frame i got it with the roof and has a arrow for the front when he removed it all bolt holes are there already. will the sparks hurt the glass. would you cut it in and at what sort of cost