I have ran Simcoe a fair amount in the past being 5 minutes down the road from it (Soldiers Bay), used to be at least a weekly destination spot, and you are correct, pressure cracks are a big safety factor that change at the flip of a switch, thankfully they are typically consistently in the same location year after year.
I have not ran Simcoe as often I used too and tend to stay in the Cooks bay area as I usually just take my kids out there now......and Simcoe has not been no where near as consistent as it used to be for freezing with our crappy winters, so now have some doubts about heading North of Cooks bay, so figured I would ask those that have ventured across it for some feedback.