I plan to replace hollow core interior doors with oak shaker-style doors that I will build myself.  If I use solid oak, each door will probably weigh more than I want.   So I’m considering fabricating some rails and stiles from a solid, lighter weight core covered with oak veneer.  What would you recommend for a stable and lightweight core material?   Besides buying new from a door supplier, can you think of any other options for my project?  

Thanks, Mark