Can't book train ride with bike, chance it?

I'm moving back home for a couple of months and i've been left with the inevitable problem of the bike.

My first instinct would be to whack it on the train (1.5hr journey, one change) but didn't know that they allegedly need to be booked in/reserved. My issue comes with the fact that my specific journey apparently isn't recognised by Trainline or Scotrail's websites, hence I'm left with two options as far as i know:

•Book bike tickets for both trains separately and almost certainly at a massive markup.

Or

•Chance it and just hop on the train without booking in.

Anyone have any experience with something similar/hopping on Scottish trains without reserving their bike?