I think that's where I got the idea of starting with the 50/50 mix. Best I've been able to tell from a lot of reading Tru-Oil is a blend of spar varnish and drying oil, either BLO or tung (as if it really mattered) though no good hints on proportions.
Did a quick check and found a MSDS I don't remember seeing before:
Mineral spirits > 56% (by weight)
Modified oil < 33% (could be a cryptic way of saying varnish, or not)
Linseed oil < 11%
