Normally 60/40 is the standard.
I normally figure the axle by what and where things are located. My main rule of thumb is one inch behind center for every foot of box. It will allow for excellent handling on highway or off road. Some believe you need tremendous tongue weight, but it is not true, also set it up so the front of the trailer is two inches below the rear, this will allow for less tongue weight, and still tow properly. I normally have no more than 85-100 pounds of tongue weight, makes the trailer easy to move around when needed. My trailers weigh between 2200-2500 pounds.
Besure you look at where things are going to go before you build the trailer. Water at the axle level gives you a better towing trailer and a much lower center of gravity. To the front, your tongue weight will be high, but will go down normally on the trip home, changing the characteristics of its handling. Putting water on the front, is the worst place for it I think.