Leah,
I would feed it the same size prey and same fequency as you would a 500 gram BP. I dont know where you heard the regurg theory. Maybe you are thinking of BCC? In my experience as long as you are providing adequate temps to utilize digestion there good. However as they become adults and slow down in there growing you have to watch that they do not become fat, they are incredibly efficient creatures. Boas are supposed to have a box shape, the body should be taller than it is wide. If you have any questions shoot me a pm or an e-mail and I would be glad to help anyway I can.