Please don't shoot under 50. Even the most experienced of us never did that. It leaves you no room for him to drop more. The correct response, when following TR and you see the 40's for a preshot, is to stall without feeding for 15 or so minutes, then test again to see if he is coming up. More details in here: Tight Regulation: Becoming Data Ready to Shoot / Handle Lower Pre-shot Numbers
Since the spreadsheet shows you did shoot that low, please get a +0.5 and a +1 and +2, to make sure he's coming up. If he's dropping, you want to know early so you can intervene with carbs.