Filling bolt holes in bed

The previous owner of my truck added some extra tie-downs to the bed, two of which - annoyingly - they added on the raised strips (versus keeping them in the troughs).

I’ve managed to remove one of them (the other wasn’t budging with my impact driver so I need to get a breaker bar or something), but what’s left is a big juicy hole through the composite bed. I want these gone so I can put a plywood platform in the bed and not have these two high-point areas.

Attached is the bolt holes and the remaining bolt.

Since this goes under the truck, I don’t want water or sand kicking up under the platform. How should I fill the holes?

 

I’d look into rubber plugs and silicone sealant.

$12 170 Pcs Rubber Grommet Firewall Hole Plug Assortment in 7 Common Sizes,Set Electrical Wire Gasket for Auto Body and Sheet Metal

https://www.amazon.com/dp/B089WGS7WM

 

Have you filled the stock drain holes?

 

I have not. Should I?

 

If you are worried about water and dust in the bed, yes. Among those holes, there are several other places dust and water can get into the bed. The tailgate and the cubby hole come into mind.

 

Will the plywood platform make these holes not visible?
I would find something solid a plastic or metal plate of some sort, cut to make it look non butchered & epoxy or silicone it to the bed / holes from below...
You could also lay few layers of duct-tape over the holes from top so tape is flush...
mix-up some marinetex or jb weld & fill the holes from underneath, leaving a solid flat / flush plug....
Thats what comes to mind..

but the do make various size body plugs, firewall grommets, etc.., to keep dust out, just need to find something that could possibly work...

 

Filling the hole:

Duct tape on underside of hole. Fill with JB Weld or epoxy. Add fillers to epoxy?

I’m not sure what the bed itself is made of, or what will ‘stick’ to it the best.

 

i like your direction better, but need to be neat about it & not slop it on, clean-up as much as you can afterwards.
both marine-tex or jb weld will work great...
Wont need fillers, stuff adheres to anything also.

 

Can you just reuse those holes to secure your new platform to the bed?

 

Yep - the OCD side of me would want to match the color, gloss and texture of the bed.

 

Thanks for all the ideas folks. I finally got the other bolt off (nice excuse to buy my first breaker bar).

I’ll post an update once I’ve filled the hole but the tentative plan is a jb weld plug. The underside of the bed where these holes are is pretty hard to reach, but should be doable.