Adding a cap on the box

I am putting a cap on my 2013 tacoma and wondering if the plastic rail covers should be removed

 

I didn't. Watch a few youtube videos and buy some quality weather sealant. Let me look for what I used on mine.

 

https://extrudedsolutions.com/

 

For most, maybe all caps it isn't necessary. The only issue is the front bed rail is an inch or more lower than the sides. That can be a challenge to fill to prevent leaking.

 

I have installed caps on a 2006 and 2014. Both times Leer stated to leave them be. I have no leaks. I redid my 2006 with simple camper tape attached to the bottom of the cap surface, doubled up front. Just like they installed in 2006. Haven't touched my 2014.

 

You might want to look into some bed stiffeners also.

 

As @Marshall R posted the front rail may give you a little grief.
It's this area here


And as @outdoorgb posted the best way to apply the weather strip is to attach it to the cap. I redid mine a few years ago and wanted to it to last. The cap will remain on my truck 'til death do us part.
https://www.tacomaworld.com/threads/rubber-molding-leer-cap.724986/#post-25821825

Finally as @Madd Matt wisely posted get some bed stiffeners. Got mine from CaliRaised.

 

No, don’t take them off. All the reputable top makers make them for use with them.

the camper shells I’ve had have always been leak free. Just double up on the weatherstripping foam on the front and it will be good to go.

 

I had a LEER camper shell and it really does require the OEM caps. When I got my wedge camper shell I put the KB Voodoo Fab flat aluminum pieces on and I'm glad I did. It looks amazing and the flat surface made it easier to install.