Hi Dan,
Seems like you are “diving into the deep end” on this. I would recommend using an output option like -o~~t~Vp, so you get two tildes followed by tabs as a ray tree terminator, and however many tabs followed by a tilde and a tab before your floating-point ray branches. Whether a tilde-tab sequence will ever be found in a 32-bit float is an open question. I remember I used three tildes in rtcontrib before it was rewritten, just to make sure confusion would be very unlikely, but they start to add up…
-Greg