Problem breeding two siamese cats?

I have two lilac-point siamese cats. I decided that i'd like to breed them to bring in some extra income. Problem is, it looks like the male siamese just doesn't know how to 'get it on'. I know this probably sounds funny, but it's true. The female is slightly larger that he is, but based on the research i've done, it should be a problem. Our female has gone into 5 or 6 heat cycles with no success. He can get the process started but can never finish the job. Any suggestions from breeders out there?