motor bike trailer plans

Cutting and shutting an old boat trailer for the son to make a bike trailer required to carry three 125 cc pit bikes. Can someone give me some direction on basic measurements,distance between the the rails that the bikes will sit on,overall length and width and centre of bike wheels in relation to axle mounting and hitch. Some photos of your own builds may help also.Cheers Steve.

^^^ thanks for that,just tried to register but they wont accept a gmail or yahoo email account for some reason.