Iron on pelmet interfacing

Timtex is what i think its called and a thick batting would help .

Me, too, Timtex. ;)

Timtex came to mind for me, too, because it has enough loft to quilt beautifully. We have a different bag lining here in Australia (I'm not sure of the name right now) but it is like Timtex. It is quite stiff and difficult to turn so the seams need to be trimmed to avoid bulk but it's worth the extra work because the bags look very professionally made.
AlmaG.

Im not sure how stiff ur wanting, but what I use on all my bags , back packs ,diapperbags is fussiable fleece , u can get it @ hobby lobby , joanns r coyh world , walmart I buy the higher one , and quilt with a close stipple design , u can see some I, ve done on my facebook sit , its unde mawmaws photos r melinda solomon, they hold up well and are machine washable , I hope this helps