I don't do 2 piece conversions. Some bowyers do build bows using them with good success, and others have had issues with bows breaking.
All depends on the riser design, woods and laminations used, etc. I know at least one bowyer that won't build a two piece out of anything but phenolic risers. Others say that adding layers of phenolic between strong woods will work. Bottom line I think is it just depends....
I'm sure some bows can be converted without problems, but I don't think every one piece bow is a candidate. Bowyers can build prototypes to try different things and find out what can work and what won't. I can't afford to experiment on customers bows, so haven't gotten into two piece conversions.