Wow, cant believe they are taking that long to dry for you, mine dry overnight on a rack in the kitchen.
You should be fine with large as long as they dont have massive gaps, having said that I know their sizes do come up slightly large as my 5yr old was messing about with the ones I bought and put on an XL OVER his trousers and did it up and ran round the house in it laughing.... hes 50lb+ and is running round in a nappy thats for 35lb+ with room to spare....I thought it was very funny!