You might consider pre-treating your sides with a veneer softener such as Super-Soft 2. I use it and I know many other builders who do. I have yet to break a side when bending.
https://www.veneersupplies.com/produ...nditioner.html
I know one very experienced builder who successfully uses Windex as a veneer softener when he bends sides. It's a cheaper alternative to Super-Soft 2.