I second that emotion what Cat248B says. I was in the end dump business for years too, and had mostly frames but my favorite trailer to me was my 36' Mate aluminum frameless.
Remember, the drawbars are attached to the 5th wheel plate, and half way up the trailer, acting as a stabilizer. Plus, you're shortening up the wheelbase as it climbs, lowering your center of gravity.
Best piece of advice I would share: Make sure the path your wheels are in once you're backed into your spot to dump is level and free of potholes/low spots. Lock the trailer brakes and let the tractor back up, not the other way around. I've literally dumped my frameless on slight angles where guys with no experience and no cahunas thought I was crazy, but it goes back to the center of gravity theory and the stabilization you get from those drawbars.
I hauled bails of scrap metal in mine for years (along with many other commodities,) and those buggers stay still until you're at the last stage before they slide. The pucker factor is quite high in those cases...
I miss my frameless wagon. Really liked the light tare weight compared to the frame-types I owned.
There's many aftermarket frameless trailer 5th wheel plate lock kits available nowadays. When I was in it, most guys were just welding 4 2" square tube blocks on the slider stands and jamming the plate level that way. Only thing is, you're in the frameless dump business exclusively unless you take the gas axe and mow the blocks off again.
I went the cleaner route and ordered the kit from Ti-Brook. It's 2 1 1/2" hardened pins and 4 bushings. The two bushings get welded to the underside of the plate up front, the other two get welded to the slider stands, insert pins and cotter pins, and you're in business.
Good luck.