Wasn't he from a shelter? He could easily be a mix. He could also be from an accidental litter where neither parents and the optimal breed characteristics.Since I don't have much knowledge on this, it's hard to tell.But from my experience, most shelter bunnies are not descended from show quality stock. It doesn't really matter when it comes to pets- Whisper is gorgeous! Are you still thinking of breeding him? That would be when I would worry about it since you don't know his pedigree.
If you got him from a breeder, did you get a pedigree? Or could you call the breeder and ask?She could also give you advice on how Whisper holds up to the breed standards.
And just remember that vet bills for breeding problems are much more expensive than a neuter. You might want to keep several hundred dollars extra laying around just in case. Just walking in to my emergency vet's was nearly $100!:shock: