How about this:
Lay up a 1/2" thick piece of fiberglass(epoxy and 1708) cut it to the length and width you want (i.e. the footprint of the pipe clip), tap a hole for whatever fastener you want to use with the pipe clips, then epoxy
chunk to the hull (make sure you thread the fastener all the way in the hold; otherwise, the epoxy
will fill the tapped hole from the bottom).
When epoxy cures, remove the fastener, and fasten the pipe clip.
It's a little more work
than gluing on with Sikaflex, but it'll hold for a very long time.
If you have several pipe clips to fasten, make a rectangular chunk of fiberglass (epoxy/1708), say, 1" wide x 12" long x 1/2" thick. Then when cured, cut chunks off to make the brackets to which you fasten the pipe clips.
I usually make a cardboard trough lined with packing tape with inside dimensions of 1.25" x 12" long x 3/4" tall (length and width vary, depending on the what I am trying to affix to the hull and how many). Into this, I do the 1708/epoxy layup
until I get the 1/2" thickness. Once cured, I tear off the cardboard form, grind the 12" stick smooth, then cut to whatever lengths I need.