Boat Trailer Overhead Deck/Ramp

I am just in the midst of designing a deck I can put over the boat when trailering so I can take the following:
2 - Dirt Bikes
1 - ATV
3 - Mountain Bikes
Some camping gear.

My trailer is tandem axle with 3700lbs rating each.

My boat is 3000lbs. So I am assuming as long as I have the weight centered over the axles that I should be okay with an additional 1200lbs.

My idea is to build a light weight (frame with mesh)deck. That can be easily lifted by two people. Back mounts will slid onto boat guides and I will make similar boat guide posts in front of the axles... Quick release pins... and some long ramps.

Then when I go camping... I can take the camper... and all the toys...

To avoid modifying the trailer... I will use u-bolts etc... to add the new boat guide mounts.

Visually... it looks like it will work no problem... since the atv/dirt bikes will be sitting directly over the axles.

I would love to do something like in the picture.. but the wakeboard tower is the issue.

When I was originally in the market for a boat I saw a Malibu with an overhead bunk for a sit down jet ski. I think one thing to take into consideration would be the height of a standard overpass and such. Good luck with the project. Make sure to post some pics of it.

Just drop the tower and go at it... if its removable just put the tower up when you unload everything else and take the top off.