Playfield positioning on Alvin G and Co

Somewhat related to a recent thread about removing the playfield from a DMD game, I'm wondering about getting the playfield upright leaning back on the backbox on an Alvin G game. On the EMs I've worked on, you just slide then forward and push them back against the backbox, and my System 11s are on a pivot.

The Alvin G has rails so I can pull it forward and sit it on the props, or I can prop it with the stick, but I feel like if I push it all the way back against the backbox it'll be sitting on the backpanel, not the corners of the playfield. Am I missing something?