Without seeing the grip on your recurve, I'm going to assume, that like many, its shape doesn't allow anything but a high to medium high wrist grip. This places the pivot point of the bow, i.e., the vertical axis, the arrow contact point on the rest or shelf and the web of your hand, all in line, and helps prevent torquing the bow with your bow hand.
The long bow, on the other hand, generally has a straight grip, (Hill style) or a slight locator grip, small indent at the top of a relatively straight grip, which, I believe, puts the vertical axis of the LB slightly forward of your grip contact point, and makes using a "high/med high" wrist grip difficult, as well as requiring great care not to torque. So, as you stated, you have to let the LB grip, seat in the meaty portion of your hand at the base of your thumb with a very low wrist, i.e., palm near vertical.
Switching back and forth can pose a real challenge, as you've discovered, as a totally different grip is required for each bow type. As mentioned by cb above, a hybrid, like a Martin Bamboo Viper, or Martin Venom, has a grip nearer to your recurve. If you have a Martin dealer nearby, you might give one a try. But, be aware that not all 'hybrids' have "recurve style" grips.
Have Fun!