I too, wanted a no drill solution and opted for a cheap 200W flex solar panel taped down with that uber sticky mobile home roof tape. It stayed on there good enough. Attachment wasn't the problem - quality was. It died in less than a year.
Regardless of the attachment method, you've still got to drill a hole for the cable.
I gave up on the cheap crap and went with a Renogy 160W rigid aluminum framed panel with their attachment feet. I put 3M VHB tape between the feet and the van roof, and then used self tapping and rubber washer metal roof screws. I also bedded them down in silicone. No leaks, no problems almost 2yrs later. I'm using an MPPT controller and get close to 10A in direct sun. More than enough to run the fridge (~4.5A) and charge the batteries. Speaking of which, I just went to 2 AGM golf cart batteries and that just about doubled my capacity to 225Ah.
The panel I used was 58.3x26.5in and it fit nicely between the A/C, bathroom vent and forward opening vent. It looks like Renogy's latest is a good 7" shorter. Might could have fit one more if I'd have eliminated the HDTV antenna, but I didn't want to.