Can I measure from the stabilizer screws to get trailer parallel

[Brettwieland]

I want to adjust my hitch and need to put my 28' Excella parallel to the ground (not level), I have been measuring from the front and rear stabilizer screws as this seems more reliable than any point on the bed pan.

However, I do not know for sure if they are mounted to the frame in the same way. Is this a reliable way to get to parallel, if not, does anyone have any suggestions?

[57Vintage]

I assume for some reason doing this on level ground is not readily accessible.

I would suggest measuring to the top or bottom of a frame rail just behind the coupler on the A frame and at the rear bumper. Measuring to the frame itself should be more accurate than any components bolted to the frame.