Hello Andrew
What you have just indicated has just "switched on a globe" in my head - I thought the guitar sims were VSTi's !! I think I have been banging on about something for 5 years when the problem is me!!- my apologies.

I have now got the guitar sims working and everything seems to be OK. Part of my problem was not inserting "Input Monitor Insert" into the tracks combo box and not unchecking the IM boxes on the Audio prefs setting once I had recorded. I hope I understand the worklflow correctly now.
Please chip in if I am still missing something.

Thank you for your patience
Roy