I'm still new at this whole snake thing, but I did the same as you with my Ana Gwyn a couple months ago. She was gaining weight and taking two adult mice, but the smallest rat I could find in the area was small adults. I offered her the smallest one I could find and she took it, but OH BOY was she stuffed! I just kept a close eye on her and she was fine. But that's when she stopped eating every week and switched herself to every other week - she just naturally did it because the prey items she was getting were so big. Her weight gain is steady and now she can take the sm adult rats just fine. (And I've found a better supplier with more varied size options so that I can size up my 3 baby snakes more appropriately in the future!)

I wouldn't worry as long as the snake ate without difficulty. But he may not be hungry again for a while!