We are aware of some epoxy boards having issues with the 3M adhesive on the decal antenna coming off after only a few surfs. The issue relates to boards that may have a coating on them, for example the Global Surf Industries (GSI) S7 Slipstream model does have a coating that effects the 3M adhesive, whilst the SUP version does not.
To overcome this, use a 800 – 1000 wet & dry sand paper to clean the underside first, then wipe clean and then test with some normal waterproof stickers for a few surfs before applying the Ocean Guardian decal antenna.
Alternatively, you could try using a small amount of acetone to clean the board first before applying the decal, however please test a small amount / area first as acetone is fairly corrosive. Make sure you clean the acetone off after with detergent and clean water.