for bending balsa I like to use a 50/50% denatured alcohol and water in a spray bottle, wet the sheeting untill its easaly bent to shape,place some wax paper on the fuse so it doesn't become wet and then pre form the balsa into he curve your after.

use rubber bands or masking tape to hold it into position untill its dry, the sheeting will hold its shape when dry, then you can fine cut it into shape and wet any small areas that need any fine adjustments with the spray bottle.
I like to use a spray bottle for material control so you can apply just enough liquid to get the job done.

some use strait water, some ammonia and water, I prefer the alcohol and water because it evaporates faster,speeding up the work time, less waiting involved.

you might need to wet and tack the wood down with some CA when your doing the final fitting, after spraying a small bit of liquid on the wood it will loosen up a bit and become flexable, but pre forming helps alot, so your not fighting the wood to get it in position, thats my method.