Bedshaped2000,
Nothing wrong with using exercise as a means of preventing post-meal high's. I often have a walk after my evening meal, more so if I have over indulged in the carbs, and I can tell you it works every time!
Exercise is just another means of reducing bg's, just the same as eating less less carbs in your meal works, both are effective in lowering blood glucose. I often inject less insulin to cover the carbs in my food if I know I am exercising afterwards, many others on the forum do likewise. Your not conning anyone, and your meter is there as a friend to tell you that what you have done is working.
Saturday nights are the one time I regulary indulge in extra carbs (chicken curry tonight) but I'll take the dog out afterwards for 30-40 mins before coming back to a few glasses of red wine, works for me and obviousely it does with you, so go for it!
Nigel