Yeah I've got the axle placement pretty much down. I'm been copying others with the same type of boat and trailer.

I've been working on it some more, We've bought everything that we need to finish it.


Here is a price break down.
Its alot but nowhere near as much as a new tandem trailer. A trailer like the one we are building would be over $3,000 if bought. So when you think of it we are doing pretty good. All of the parts we are adding are brand new, the only thing left of the trailer is just the metal frame.
That saved us some bucks by using it instead of building from scratch.
When we are done this will be a brand new trailer

Trailer cost $180
(1) a-frame coupler $29.99
(2) u-bolt kits @ $16 ea. = $32.00
(1) jack wheel $20
(1) bull dog jack $29.99
(1) tandem axle hanger kit $39.99
(2) 3500lb trailer axles @ $169.99ea =$339.98
(2) pair leaf springs @$39.99 ea = $79.98
(1) wiring kit $13.99
(1) winch $12.99
(1) winch strap $9.99
(2) tandem fenders @ $69.99ea = $139.98
(4) tires/wheels @ $94.99ea = $379.96
(2) tail lights @ $9.99ea = $19.98
(1) center light $12.99
(2) marker lights @ $4.99ea = $9.98
Steel for bunk mounts $75
hardware (bolts) $10

total $1551.71 after tax.
Its alot, but cheaper than if someone else did the work.
Not too bad for a new custom made tandem axle trailer(heavy duty).

pics...

new coupler..