Geoff, the problem with the stroke foot plate in Sallyport is the same issue of jumping out. The right hand arm is short and when in rough water which shifts your balance tot side the foot plate slides too the right and then the left side jumps out. This got worse as it was raining and slippy. I fell off my seat as it flew out on a rouge wavelet.
I think eventually this foot plate needs to be replaced if possible. I think on clam harbour rows it's fine, it's the rough racing waters, where it becomes obvious.