between the slider window and the body

I'm just about to pull out the side slider windows, clean them up, replace the channel and add some tinting to them for privacy.

In re-fitting them I'm wondering if I should put some foam tape or sealer between the window frame and the body to prevent water dripping through. I've got a slight leak on one side that I would like to avoid in future.

Any thoughts?

In the fitting instructions for my windows it said to put a bead of silicon all the way around to make them waterproof.

I was thinking that but then thought it might be hard if I ever remove them again. So was thinking foam or mastic or something. I'll keep looking and use silicon as a fall back - thanks.

Mine have a white foam/rubber tape around. I presume from new. It's about 1.5mm thick.