single axle tractor, tandem axle trailer... weights & loadboards

Been looking at doing something little different a 389 peterbilt with single drive axle and a 25k lift axle 70 inch sleeper and 500 hp i have seen some like this not 70 inch sleeper tho I'm a grain hauler looking to lighten my truck up a bit just was wondering some thoughts on a combination like this

 

Why only 1 mention of king pin in this 3 page thread? Just because you have a tandem axle on the trailer does not mean you can haul 34,000 lbs on it. Inner bridge determines weight - along with tire size and mechanical components.
Sliding axles forward will reduce the weight.
http://www.statepatrol.ohio.gov/doc/truckbook.pdf page 44, 45 46.
Pg 44 shows a semi + trailer. 4 axles with inner bridge distance of 36 feet = 66,000 lbs max weight.
that means 33,000 lbs per tandem.
Single axle cannot weigh more than 20,000lbs (OH example. Montana is the same)
Pg 45 shows 34 feet between them. down to 64,500 lbs or 32,250 lbs per tandem.
In order to put 20,000 on a steer axle (or excess weight on any axle) axle and tires have to be rated for it and a special hauling permit purchased. Look at safety weight rating on the tire (and double it for 2 tires) will give you one option for weight rating for the steer axle.