Wow Andy, fours are amazing! You're doing better than me, I've had some fours but mainly fives. Remember, normal glucose, for a non diabetic, is between 3.5 and 5. Four is not "hypo". Different for type 1 diabetics, they would have reason to be concerned with a four because they are artificially injecting their insulin and might have injected too much. All your fours show is that your control is fabulous and your insulin resistance has much improved. If you are not feeling unwell (and there's no reason why you should be - my strapping rugby playing 16 year old son has just tested his sugar for fun/curiosity and it was 3.8) then probably the only thing you might do is discuss with your doctor next time you see him whether you need to be on quite so much Metformin. As for exercise, well maybe have a small snack beforehand (but protein would probably be better than carbs because it is slower releasing of glucose)
Type 2 on Metformin, diagnosed Jan 2013, ultra low carber, Hba1C at diagnosis 8% (64), average BS now between 5 and 6 mmol.