Because the double ball system is so rare, there aren't many options out there for us headless guitarists. There are adapters for the head but I haven't converted yet, so for the time being these are the best strings I can get for my Steinberger.
I've also tried the D'Addario double-ball set which I found to be surprisingly bad (and doesn't even fit an R-Trem properly)! These ones are okay, my first 2 sets have rusted a bit fast compared to my usual single-ball strings and the unwound strings felt perhaps too light for their gauge. If your headless can take single ball strings then pick your favourite set of those, don't bother w/ the double-ball ones. Otherwise, these are the best in that category.