Planting different types of velvet beans together

Is there a problem in planting tropical (vining) and bush velvet beans in close proximity to each other? We would like to save seeds and want to preserve the characteristics of each type of velvet bean.

I’ve wondered this as well in seed production here at ECHO in Florida. It’s difficult to find confirmed information about an isolation distance between different varieties of velvet bean (Mucuna pruriens). Some sources say it’s self-pollinating and doesn’t need isolation, but I’ve read other sources that say it needs isolation because of bees. I’ve noticed bees visiting the flowers but because the flowers are often under the foliage and close to the ground it doesn’t seem like there is as much bee activity as if the flowers were more exposed. I still try to isolate varieties (500 feet or more) to mitigate cross-pollination and keep the lines as pure as possible. We have seen some mixing of genes in later generations of seeds that were collected off the farm (not produced for seed but grown as a cover crop) so crossing is possible; I just don’t know what the best distance is for isolation. I wouldn’t grow it in the same field though if you want to preserve the characteristics. Anybody else have thoughts or experience with this?