Drilling a hole in a surfski?

Would it be OK to drill 2 small holes in the top of the double footwell partition of a carbon/kevlar ski to mount a GPS? Just big enough to fit a zip-tie through. Thanks.

Yes

Hole is a Hole so maybe a little silicone sealant around yer zip tie !

I'd rather glue something on the ski, and drill a hole in that something...

From local electrical supplier you can find something called a cable tie mount. Made of nylon, they have a low profile, come in various sizes with or wihout foam adhesive. Use a size about 1.5" to 2" square. The adhesive is not good but the double face adhesive tape used for car body trim is very good. Your installation will be reversable too.
The cable ties should be trimmed flush with a sharp knife- or else the sharp ends will trim some part of you.