extension jambs for half round
#1

I have installed a half round window but need additional extension jamb of about 4 inches...the wall is 10 inches thick so the 6 inch jamb that came with the window is not sufficient. Any ideas on how to make Jambs for this window. Thanks
#2
Across the sill is easy, since it's straight. Check the moulding and trim section of any big box store or lumberyard and you will find window stool. For the arched section, you can cut strips of 1/8" plywood (luan works, since it has no knots and virtually no other defects) and bend them in place, one at a time, until you have the desired thickness.
#3
There are also flexible mouldings that are a bit costly and maybe not easy to find. Start with this website: http://www.flexibletrim.com/