Are you too posh to just throw a mat on the ground and lie underneath the parasol? I mean you get on your back to do an oil change on your GT86 dont you?
Don't even have a spare mat to roll on the ground either haha, its currently being used as my floor protection for my gym in the living room.
I did use it a few times to work underneath my Mazda 3 MPS though a couple years ago.
I've not gotten underneath my white GT86 but I did on my black one back in 2015-2016, where I did try to do my own oil change and couldn't undo the sump plug.
I don't have me 86 now, I am a civic driver now. Haven't found the need to go underneath though as I've found decent garages/specialist for reasonable price around me so i've kind of not bothered doing any servicing now.
I will try and install mods on my own though if its doable, most DIY i've done on any car was on my MPS:
1. Changed gearbox mount
2.Changed high pressure fuel pump
3.Turbo inlet pipe
4. Replaced boost controller solenoid as I snapped the original
5. Installed short shifter plate