Well, even if you could legally build it based on his circuit, I don't think it'd be right to do so. Anyhow, I can't tell others what to do, I just know what I'll do.
I can only recommend allowing for a crossfeed daughterboard mount. People
using crossfeed are minority anyway so it's just an inconvenience. You can
always build it on a protoboard, it's simple enough, and just add it to the amp in that form.
Also, even if it's "legal", you might run afoul of Head-Fi policies. Head-Fi
policies are much stricter than the law and as Jan is one of main sponsors
if he complained I'm sure this thread wo go poof (if it contained crossfeed). I'm actually quite surprised this thread was not brought on Headwize, as Morsel herself stated during ppa development days that she will do so because a lot of people protested due to percieved "commercial" status of PPA. Also, there'd be less "noise" on the thread. Though right now I'm probably making some myself.
By the way, MOSFET should be biased to the most linear region, and it should be more than the load will ever need to use. cameron made a good point
that ground channel might need to sink 2x.
10 Ohm might indeed be a bit much. I say experiment.