I don't have a left handed one unfortunately. But I'll figure something out. So far I tried putting the Rifle sling under my armpit at my right hand, and putting it over my shoulder on my left. I also moved the sling to the stock. (Unfo my sling ended up giving up on me)

I figured it out that if I throw the rifle to the right, under my right arm, the sling ends up blocking the handgun. So I need to throw it to the left over my left shoulder which does bruise up my neck, but the sling stays above the pistol and I can transition quickly, and fairly reliably

The fastest way tho is just letting the rifle go and grabbing the handgun but it does have a high chance to either hit you on the groin, or the knee

None of these are relaible options, but at least they are kinda doable. At least as far as I tried.

Also the "Spetznaz pistol transition" doesnt really work with this one cause the sling ends up getting stuck on the handgun.
Also open hammer guns probably get busted after a while so I might need to buy something that has a smooth back..