I do the same thing but I don't use tab. If the dog is to slow on the recall I start jogging backwards saying heir to speed up the dog and then one praise like good. You can see the dog getting more excited about it by doing this and they will come right to you fast and then sit right up on you. If the sit is still not as close as you want then just take a couple steps back saying heir and as the dogs sits where you want say good and step back again with the heir command and after the dog does it right again then release with a big praise. All this is doing is getting the dog to understand want you want him to do and he is doing it right on his own with no corrections. Repeat doing this to give the dog a clear understanding of what he is supposed to do and he will do it the correct way with excitement.