I've done over 140,000 miles with the unmodified auxiliary feed line. The rocker shaft doesn't wear at all and the oil pressure is still 65 psi @ 2000 rpm fully hot ( oil cooler with 'stat is fitted ). I just fitted another one to my trick engine with the wholehearted approval of my engine guru ( whose like in the US can be counted on the fingers ). I got the feed line kits from TRF, and don't know their source.
The only problem I've had is sealing the banjo fitting to the head. According to my engine builder an extra copper washer is needed to keep the bolt from bottoming in the head ins