I think that the close meander I did in the quilting makes them stiff enough without using timtex or interfacing but maybe that's an idea instead of such close quilting. How does the timtex react to the curve of the bottom of the bowl though? I purposely quilted this area a little more lightly to make it more flexible then quilted the actual base of the bowl heaviest of all. I think this gives a really nice shape. I've only used timtex to make postcards but it's very stiff, I found.