I'm sure you know this already, but just because you can't feel it anymore doesn't mean it isn't working anymore. As far as going to 50mgs in a single sitting should be fine. I've gone that high on multiple occasions and nothing horrible has happened, other than some nasty anxiety sometimes.
The highest I've seen guys go and be relatively safe was 75mg, but I'd stop at 50.
If I were you I'd go to 50 and have a moderate workout and see how it felt.