MM, I have both a slanted door bar like yours ( although higher at the B pillar) and a horizontal swing out door bar.
To make this work I have a double net with the top one dropping down to the horizontal bar and the bottom one from the horizontal bar down.
I have had no problem with tech inspections as I had them both custom made to make sure there are no places where my arms or feet can protrude.
I would not, however, want to imply that this excludes any car from the lateral helmet support rule.
What I am currently working on is a removable extension for the driver's side helmet support that incorporates a " slide in" male/female reciever with quick release pins.
As my previous sentence states, if I can make it work, you would climb in, then slide the extension in place and insert the pins from the driver's inboard side with large pull rings (I wear SFI 20 gloves) so for emergency egress the driver would simply pull the pins, pull the extension forward, and hopefully quickly emerge from the cage.
Quite frankly, if this doesn't pass muster, I am a dead duck.
I have spent about eight hours trying out different attachment method's and nothing else will allow me to climb in or out with my helmet and head/neck restraint on. If you are on fire, you don't have time to try and remove your helmet which in my case is nearly impossible anyway.
For a rule intended to increase safety, this one is a definate Edsel.
Without trying to be a alarmist, I fear someone may suffer dire consequences from this rule.
Since Kiwi Steve seems to be the champion of this rule, I would like to invite him to post how he think's this rule should be interpreted in tight situations like yours.
This has been my gripe for years...rules being implemented withoout having reasonable knowledge about implementation and effect. Bob