Sureply plywood

Has anyone ever used this in a build?

https://www.patriottimber.com/plywood-lumber-products/sureply-underlayment/

It's 1/4" thick and uses exterior rated glue.

I know the 1/4" would need plenty of support, for walking on, but let's say you had plenty of foam and framing to allow for that.... what do y'all think?

I forgot to mention... the boat will be stored indoors.

As an underlayment the plywood is probably not structural. Underlayment is intended to cover subfloors to create a better surface for other flooring materials such as carpet or tile. If you intend to cover a solid foam surface you might get away with it. If you intend to use it to span framing members as the floor material, I don't think so.

If you're trying to save money, I doubt if most boat projects seen here use more than two sheets of flooring. The cost difference on a couple of sheets of plywood isn't worth the risk of having to replace it. If you are trying to save weight there are alternatives - although all probably more expensive. Aluminum sheeting is one, or PVC sheeting.

Boy, if it is in your budget, why not double the 1/4" to 1/2" with two layers
spot glued together with construction adhesive ??
put the direction of the grain opposing each other, or "criss-cross".
Then, you would have tremendous strength and no soft spots.

just a thought.

Cost is a concern, but weight is a bigger concern... I live in the mountains and tow with a 4 cyl car. I also have to move the boat in/out of the garage/driveway by hand most of the time depending on who is parked where on the street and my shared driveway.

I know I'll be upgrading boats in a few years so this is not a "no expenses spared" type of boat conversion.

My only gripe with aluminum floor/deck (besides cost) is the heat factor. I don't really want to add seadeck or similar foam... more cost.

Is the PVC panel you mentioned the FRP bathroom panels at Lowes?

I stopped by lowes and looked at the frp panels... They are way too flimsy to be used for a floor unless you have a very solid foam support layer underneath in my opinion.

The PVC product I referred to is brand-named Sintra. I used it because it's light weight. I used one sheet on my 1236 project. Too expensive to use if multiple sheets are required although many here spend a good deal more on aluminum. If you want more info on how I used it:

https://www.tinboats.net/forum/viewtopic.php?f=21&t=9712&hilit=+lowe+1236

1/8" aluminum is what you need. Sure it is more expensive but not bad considering it will last forever. I see a lot of plywood used in builds but I don't care what you put on it it will eventually rot and you will be doubling up on labor. The best thing about aluminum is you can cut it with wood blades on a circular saw and pop rivet everything.

From what I've found, 1/8" aluminum sheet weighs about 1.7 lbs per square foot, and 3/8" plywood weighs more like 1.0-1.2. That's a pretty big swing in weight for my project.