I wire tied mine, though with steel wire instead of copper.

The biggest problems I had was learning how to do it. As in just how far away from the edges to get, and how far apart to drill the holes. Sounds like this was your problem as well.

I went about 4" apart along the belly areas, and got as close as 1/2" apart at the ends. I was typically drilling about 1/4" up into the plywood. I discovered that by cutting the pieces of wire about 6-8" long, and bending them into a u shape I could quickly insert them from the inside.

In stitching the boat I ran a number of them lose at one end, and then ran them lose about a foot apart until the other end, where I tied several more for the load of the curve. All were *very* lose. As in barely able to hold the pieces in position. I could then roughly tighten them to get some shape, and start filling in the rest of the stitching. It went pretty quickly and easily for me this way.

My clever tightening tool was my little needle nose vice grips. As I would tighten up some of the very lose stitches, I would simply grasp much further up near the boat and give a few twists. I could twirl nicely by simply twirling the knob at the end of the vice grips.

I rapidly learned I did not need to "tighten" wires. By walking up and down the seam taking up slack I would achieve a tight fit. My mistake was in ultimately snugging up everything, forgetting that my panels were not perfect, and thereby sewing in a few bulges by tightening areas that I should have left slightly gapped. Not a big deal, but I was aware of it, if only to late.

If your plastic ties are sewn in well up, so that covering them with a fillet would require 30 lbs of epoxy, don't do it. You don't need much to make a decent fillet, so going between the ties and cutting them out and finishing probably makes the most sense.