Yes.
.....Only kidding.
The idea that Catskill's sit on the tips of their hackles and the tips of their tails with the hook supported out of the water is ludicrous (I'm not saying you said this, but one reads this all the time). I doubt that after one or two floats that a Catskill even sits higher than a modern thorax pattern.
UK, flytier extraordinaire Ian Moutter has even argued that Catskills work because they are reasonable imitations of emergers. That tight, unflared tail doesn't stay above water, but rather goes underwater and represents a shuck. An article in Fly Tyer about 18 months or so ago, showed this exact same phenomenon.
FWIW, if you're not interested in the emerger aspect, I would tie the tails flared. From the trout's perspective, if the tail remains on the surface, I would imagine (I'm not the only one, this isn't an orginal thought) that a tight bundle of tail fibers doesn't really represent tails but rather a continuation of the body - effectively turning a size 16 into an 8.
My two bits.
-Steven