Set up for harai goshi to the offside

Hi all. I'm trying to work out how to set up my favourite throw and would appreciate some help. I've developed a strong harai goshi to the left side as a right handed player. I use the left underhook and right collar grip, and it mostly appears when someone throws a big overhand. It basically developed as a product of an injury, where I couldn't balance on my left foot especially well, so ended up only being comfortable throwing left. This has all healed but I'm still much more stable standing on my right - so my uchimata and ouchi throwing right are almost always hopping. Rehab continues but the stability will probably never by symmetrical.

My main issue is that I find it hard to proactively execute. It's often in response to the previously mentioned overhand grip from my opponent, which makes finding the underhook really easy. Does anyone have any good advice on how to set this up? I mainly find getting to the underhook pretty difficult, so perhaps an armpit grip rather than underhook and trying to throw osoto-gari to the left would be a good plan?