In the Therion Map Editor, I have added a background image for the Extended Elevation. This was created from PocketTopo data. This image extends Right.
I have created a Scrap with type Extended, but Therion seems to be assuming the survey stations extend Left.
Hence Therion attempts to invert my scrap and the output makes no sense whatsoever!

I've had a look to see if there is a Scrap option to extend right - there isn't.
I changed the Scrap scale for negative X pixel dimensions - no effect
I changed the Scrap scale for negative metres dimensions - no effect
I tried reversing the extend left/right data in the .th file and it scrambled how the stations relate to each other. In any case, this doesn't seem the right thing to do as it was also sourced from PocketTopo.
Yes, I've Googled and read the Therion Book.

Your 2p would be greatly appreciated - thanks 
I must be missing a trick!

There is an option to extend left or right somewhere but off the top of my head I can't remember where. Have you trawled though the wiki as loads of good info on there. Also use the searchable mailing list this goes back years and is invaluable.It's always my first point of reference then the Therion book which can be hard to follow sometimes.

Swallowneck said:

There is an option to extend left or right somewhere but off the top of my head I can't remember where. Have you trawled though the wiki as loads of good info on there. Also use the searchable mailing list this goes back years and is invaluable.It's always my first point of reference then the Therion book which can be hard to follow sometimes.

Click to expand...

Cheers 
Yes I Googled and read the Therion Book, but found nothing even close.
Andrew Atkinson suggested I join the Therion List and ask there; joined and will post question shortly.

What I'm still struggling with is that the route from PocketTopo to Therion has so few options that it ought to just work!
I still feel I'm missing something simple that will totally solve the problem.