I'm sure I read this somewhere but please correct me if wrong.

when moving a ship (especially one that collides) you trace the ships movement along the template via the back nubs not the front.

this has obvious problems with big ships and small templates.

I also see the logic. Eg if two shuttles are near each other and one performs a hard 2 but collides then tracing the back nubs the shuttle may only manage to turn 20° instead of 90°, this makes logical sense to me but others I asked dont seem to have heard of the rule,

can someone please clarify/ confirm this

In fact, you use both sets of nubs.

The template must remain centered at all times between both sets of guides while you perform the backtrack.

The practical effect is that, as you correctly guessed, ships may not be able to fully complete their turn/bank maneuver when they overlap another ship.

I ran into this issue once doing a hard 1 turn with a falcon that overlapped and having the template lost somewhere under my base. I wasn't sure on how to orient the falcon correctly without using the guides.

I did see a game on vassal where a lambda was doing a 1 bank and was trying to line up with the template in much the same way. The player used the 4 straight template and attached it to the front of the 1 bank template (and a copy attached to the back). This allowed for the nubs to be used to orient the ship along the angled flight path.

You can try the extension method or find the ghost button on your mini's base.

I went and got the appropriate rule from P.17 to help answer your OP.

"From the opposite end of the template, move the active ship backward along the top of the template until it no longer overlaps another ship. While moving the ship, adjust it so that the template remains centered between both sets of guides on the ship’s base. Place the ship so that the bases of both ships are touching."

*added rule

Guess.