Walter,
Thanks for the potted explanation of TANS but I am reasonably well versed in it's use having flown using both Mk1 (Decca) form as well as the Mk2 version. I also flew RAF SH before it was available (the pleasures of changing Decca chains and turret key swaps etc half way along a flight, not a sensible navaid for a 145 kt machine, but I digress).
There is no suggestion that a usable DME beacon was available, other than your theory that a portable beacon might had been laid for this flight. I said it probably wasn't, based on almost 20 years of RAF service but what would it prove if it were? The crew may have actually very little in the way of navaids on the flight. We don't know because there was no conclusive evidence one way or the other.
Regarding the speed question, the Boeing simulation was just that, based on a simple time/distance calculation on other estimates. No way can this be held up as substantiated evidence. It could be argued that it was in the aircraft manufacturer's interest to offer up nothing other than a continued high speed for the whole crossing. I cannot readily believe that a crew, especially one of their calibre, did not do the one thing that is second nature to all SH pilots. If you aren't sure if you can maintain visual flight you slow down. This ethic is drummed into an individual from day one of pilot training, it's so basic because it is self preservation. The only real evidence was given by the yachtsman in a statement and he said the aircraft was going slowly during the time he saw it.
Sorry to be the one to say it, but I don't really think that trying to invent new theories provides much value at this late stage, especially ones involving US Navy Seals searching for special equipment, second Chinooks in the area etc. Sorry not to be of more help in that respect.
P.S. I think that Mr. Malik's article has it all just about spot on.
ShyT