Can't say for sure if mine is OG - but I think so...
It looks like the bolt should turn to reduce/apply tension - but it does not. The method I used is when the roof is UP the springs are at their most loose - so support the roof up with wife or bit of wood, fit strut
with slight pressure - job done. If you try to apply more pressure when UP (and you can by pre-turning the springs) there is a frighteningly amount of pressure when roof is down - I felt too much to be safe, and to open
the roof easily you do not need the extra power/tension
This is old photo with bolt out, the far side that you can't see is captive - so doesn't rotate once fitted - and as you can see the bolt on the outside is simply a bolt - no adjustment
Inside pull tags use aluminium nuts/bolts - I think all OG Dormobile screws were al. but newer replacements from Dormobile are stainless
Roof held on with aluminium bolts - I plan to replace mine with s/s at some point - I can't explain the rust marks maybe the hinges are steel ...and to me it looks like mine are fitted the wrong way - ie
bolt heads should be on outside...?
Hope this helps....