Big discrepancy in finger strength - one arm vs two

Hello everybody,

I have recently realized that when doing hangboarding, my one arm hang strength severely lacks behind my two arm strength, and am looking for advice from people who have overcome this discrepancy.

For reference, I would describe myself as a solid 8A/V11 climber and have done one crimpy 8A+/V12. In general I prefer crimpy climbs, but always felt like my finger strength is at most okay for my grade. I'm 27m, 65kg bodyweight. I haven't done any training since last year April except 'just climbing' since I've been lucky enough to do most of my climbing outdoors. The other sessions were either the Moonboard or easier climbs in my gym.

During the winter time I decided to do the lattice assessment to check in with my weaknesses after a long outdoor season, and was very surprised by the results: While my two arm strength is actually on par with average 8A+ climbers, on one arm I am at a ~7B level. I can tell from the climbers I usually boulder with around my level they have a much easier time hanging one armed, which seems to agree with the assessment.

This somewhat correlates with my feeling of being relatively weak at campusing on smaller holds. For example on the famous 8A+ 'Jacks broken heart' I struggle hugely with the first campus move. Even though for most people it's one of the easier moves for the boulder it's definitely my crux.

In general my upper body strength is decent (I can do 2 pull-ups with +45kg or 25 at bodyweight). At 90° I can do a lockoff for around 10s, a bit less at 120°. On a good day I can do a one arm pullup.

While I have no issues hanging from a bar one armed with engaged shoulders (even with 10kg added I can still do scapula shrugs), this to me seems to be a shoulder/wrist stability issue more so than fingerstrength. I should note that I feel a tiny bit stronger in a lockoff compared to straight armed for this test, but not meaningfully so.

I have done some sessions with straight one arm hangs now, and can feel my arm shaking and my fingers opening up towards the end of the later reps. I've been doing 6x10s hangs with -15kg, which is around 90% of my max. Any advice to improve on this (except just doing the exercise) or similar stories?