if you train realy late and only have time for one meal after training i would use a faster acting insulin Humalog as its out of your system in a couple hrs. Eat your normal meal pre-training doesnt need to be a ton of carbs , 50 would be fine , the intra "shake" is clear liquids not a heavy shake , just BCAA's glutamine and creatine with some sugar , the intra shake is an importaint part of the puzzle. Post workout have your meal , again 50g carbs would be plenty.
so with your pre training meal intra drink and post training meal you have about 125g carbs which is plenty enough to cover 10iu slin that you shoot preworkout.
ALL that said , i would personaly eat your preworkout meal alot earlier , no sooner than 1.5 hrs pre training , i think this will help ALOT with you getting sick from drinking somthing during your training as you body is still trying to digest that meal when you start taking blood away from the stomach and intestins to fill the muscles which can make you sick.
So eat an earlier meal , shoot your slin before you walk into the gym (humolog) , start sipping your intra BCAA drink , imidiatly post workout drink a shake with 50g protein , 50g carbs followed by a meal 45 min later with say 50g protein and 30-50g carbs , by this time you have had all the carbs you need to cover your slin and the slin is no longer active