I would lay the batting out, spread one layer over it, right side up and pin it profusely (closed safety pins, of course). Put on the other layer, right side down, stitch the edges as usual, turn the quilt, smooth it and remove the pins as you tie it. The batting you are using now is softer and has less body than the Warm and Natural (which is why I like it better than W & W), so pinning should take care of the issue. On the other hand, have you considered a poly batting? Some of those have less 'give'.