they always show them spread apart on camper-style double tongues. is there a loss of function if put together on either side of standard boat tongue? also, do they interfere with surge brakes?

I can't answer your question about single rail vs double rail application, but do know there is more than one company manufacturing surge brake compatible systems. Do a search and several options will come up.

I too used to think they wouldn't work with surge brakes. Was quickly shown to be wrong. I'm glad too. I'm getting ready to purchase one for the new boat.

Buck

i am thinking, if u angle the chains back a little bit, something like 15 degree angle, they will hold weight up, but get effectively longer when hitting the brakes to aviod stopping surge actuator from compressing.

Do a search here on OSO on "Weight Distribution Hitch" I've posted on this a lot.

They work great with a Pole Tongue Adapter. etrailer.com sells them, as well as many others.

They CAN work with surge brakes, but you MUST have it set up properly to not interfere with coupler movement. Also, you cannot use traditional sway control with a WD hitch.
They work PERFECTLY with Electric over Hydraulic brakes (EoH) or Electric brakes.

BUT, you can't band-aid a crappy towing setup with a WD hitch. You still must have a truck rated to tow your load under all capacities, and have the trailer setup with proper tongue weight.

speaking of electric brakes; what happens when u dunk them in salt water?

[QUOTE=Sydwayz;4075906]Do a search here on OSO on "Weight Distribution Hitch" Also, you cannot use traditional sway control with a WD hitch.
Can't use sway cont with WD? or surge brakes? or both?

Can't use sway control with surge brakes. Ideally, would not need sway control with proper setup trailer and WD hitch (if needed).