Without going custom, it narrows the hunt in finding an exact fit for both riders. Though lots of variance can be made with eccentric bottom brackets, adjustable stems, and seatpost having extra adjustable set-back.

I'm still tweaking ours! I've even considered adjustable track stem for capt., adjustable stoker and forward mounted seat post.

Ps. By chance is there a nearby place to rent, test ride tandems? Just so you both feel its something could work in sync or better word... harmony