This is the information posted on the 11th December following experiments carried out by TrainDriverJohn
I think you guys have got it all figured out already but I did do a few experiments.
Loco R3284TTS Railroad Flying Scotsman (no Carraiges)
Straight test track (cleaned with good connectors}
RailMaster Program. 75 seconds consisting of sound on/off use of function buttons (whistles) forward to shunt then acceleration and deceleration commands before stop. The programmed returned journey is exactly the same except the program is using reverse instead of forward.
On each iteration the loco was placed back on the start line.
The results are:
1. It is obvious that it is impossible to know where the loco will come to rest on any given journey.
2. The return distances are considerably shorter. I believe this to be due to pushing the tender rather than pulling it. The variations are the same though so on the return journey you could compensate for this by placing extra time in the return journey program to bring it back closer to the start line.
3. Even after doubling the journey the variation remains similar. It would therefore be reasonable to conclude that any distance would produce a similar result.
4. After trying 41 iterations it appears that you would have to have at least 44 mm from the buffer after having recorded your shortest distance.
5. Further experimentation is needed to establish if it is possible to have reasonable tolerances and therefore is a practicable use of this type of program when the loco is not returned to the start line on each iteration.
6. Further experimentation is needed to establish what would be the outcomes if a load was attached to the loco. This might just result in the conclusion in 2. This of course would mean that if you had a terminus to terminus journey you would have to stick to the same configuration or a change in the program times would result.
7. The loco running could be interrupted any time dirt on the track etc. this would almost invariably give a result outside of expected tolerances.
8. It is already looking like an alternative method to this may be a better idea. Nice try but no cigar.
9. Of course all the old hands knew all this and have already been there done that.