EZ-Plugs

[Capitan Jack]

I just put EZ-plugs on an SUP to provide anchors for a bungee.  Others have had problems with them, so here is my 2 cents.

The bottoms of the EZ grips are flat and they don't bend, so you have to find a flat spot or they won't stick, or if they do you will have some air under part of them. 
Now finding a flat spot is tough, you have to be 5 inches or more from an edge to get even close to flat.
If you are having trouble, I found that the urethane equivalent of epoxy can help make up for any curvature and provide a decent adhesion.  This stuff is white or cream colored, so plan accordingly and don't use the transparent EZ grips.  When it hardens it can fill a gap caused by the curvature.  Hardman Double Bubble Urethane Adhesive Purple Beige Label A85 Water-resistant (Hardman/Kalex #42024  available on Amazon)

[Badger]

I put EZ-Plugs on one of my first boards. Surface prep is very important. They are still holding ten years later. For another board, I went with the soft NSI tie-downs and liked them better. They don't require a flat surface and stick extremely well.

https://www.northshoreinc.com/store/pc/viewPrd.asp?idproduct=344

[PonoBill]

Ditto on the superiority of the NSI tie-downs. The only problem with NSI tiedowns is you have to be certain of the location before you let the tie-downs touch your board. Once it's on, it's on. Immediate scraping might get it off, but after even just a few minutes, the hot coat or paint will pull off before the adhesive does.

[sflinux]

I agree with Badger regarding surface prep.  I put them on a board to make a tail handle.  The board was painted so I sanded it down to the carbon layer.  I used 5 min epoxy resin, and put excess so it formed a pool to cover the borders of the EZ-plug.  Never had a problem with mine using the Beasho elastic tail handle design.
https://www.standupzone.com/forum/index.php/topic,25430.165.html