I have made bows with one limb reflex and the other straight,, it is not that hard to tiller,,but I think as Jawge said starting with the same shape may make it a bit easier,,,I usually put the limb with most reflex on the top,,, back when I started making bows,, alot of guys thought that steaming or heating the wood had a negative effect on the wood,,,,, so I made alot of bows just like they came out of the stave,,,good practice for sure,, but a little heat can make life alot easier,,