I have a Toyo 45G and did some testing with a Nikkor T ED 360/500/720mm lens that was mounted in a Linhof Technika board, itself mounted in a Toyo-to-Linhof adaptor.

Test procure: grab the lens and apply force to it.

Results: there were two places of movement. The first was in the tripod head, particularly the quick release plate. The second was the Linhof board moving in the adaptor. Both of these occurred only when significant force was applied. There was no movement in the standard itself nor any flexing of the rail (the rail being the short base rail with one short extension attached).