I would go with the concrete tub style rack you can find a DIY easily.

that is not my rack but you get the idea..
The tubs are 28x20x6 and I just figured out where to get them in canada, I have been looking for months.. Here ya go:
http://www.homehardware.ca/Products/...tc_40l_28x20x6

you may have to have them order them for you but they dont charge extra and have them to you in under a week. I have also tried kitty litter pans with success.

while your at it dont forget the watering system. Brian at grandview rabbitry is the best source I can find in canada.
http://www.grandviewrabbitry.com/wateringequipment.html

I do 1.3 in those tubs. Depending on your males you can keep them in with the moms but if they are aggressive I pull them.

hope those links help you out.

Good luck!