Never done that with the body on. If you can access the nut on the top of the strut, then you ( maybe ) could undo the lower suspension ( mostly.. you just want everything loose so that it's easy to take apart, and allows the control arm to swing down as far as possible. If you actually undo everything then you will not be able to stabilize the strut to preload it with a jack ) ) and raise the car up ( The chassis needs to be higher than it normally would for the suspension to swing down far enough to unload the spring ) then preload the suspension and use an air gun ( or electric impact gun, mine works just great! ) and release the top nut. then drop the car down onto some sort of block then keep dropping the suspension until the spring is under no load.
Undo the lower control arm the rest of the way and remove the strut. Replace the shock ( a job in it's self if you don't have a vise to hold the strut to undo the shock housing nut..) A gas shock works well for reassembly using this method, as it will always want to extend, allowing you to get it into the hole in the upper strut bushing which is still in the frame, and that can save you a few tries..
The disadvantage of this is the possibility of the car falling during the operation ( maybe on you ) and I'll bet you will not be able to remove the upper bushing and replace it ( which would be a good idea..)
The regular Elans have a hole above each rear shock tower to get at the strut bolt. I would imagine that the Plus 2 does as well.
Unless somebody has another way, body off is the next choice.. then it's duck soup ( you may find it easier to compress the shock on the car rather than using a spring compressor, depending on the access you have, both body on or off..)
Have fun ( Mark cackles and moves away with a Quasimoto limp...)