What's the rush? This breeding season, next breeding season? What's the huge rush to put weight on this male? If he's ready, if she's ready...they're ready. She's not even at 1,500 grams and that's also dependent on her length (1,500 is not the only number to worry about). Weight is only one of the determining factors anyways. Has this female finished her quarantine period? She's a rescue, is she eating well and in good health? Rescues often take awhile to get back up to speed.

Breeding isn't about rushing into things or trying to push snakes too fast just to hit a goal you have...no "ASAP!" about it, at least in my opinion.