Let's see.... I really do like a nice, beefy fabric as the inner layer... it adds some nice shape to the bag, but at the same time has a softer side that I don't think could be achieved with interfacing. I think also that a beefy inner layer (I can't remember exactly what I used in the bags I made... but they were cheap bottomweights) gives it a nice weight.... of course not heavy, but with a bag such as this (which is on the larger side, yet not cumbersome), it needs a certain feel, I think.
I didn't put interfacing on the inner pockets on my personal Nappy Bag and now I'm almost wishing I had. The pockets are incredibly deep (which is great!), but often to get something at the bottom I have to really, really reach in and even though the material is doubled up on the pockets and I used a really nice (re: expensive batik) quilter's cotton on the lining, it's started pulling away from the inner layer in places and that's quite disheartening. I think the interfacing in the pockets would have added more stability and strength.
Oh, and for the inside, while I can totally appreciate a nice-looking inside, I would go cheap! These bags are TOTAL fabric suckers and before you know it, you can drop a mighty big chunk of change in fabric expenses if you don't watch your budge!
Hm... I can't really think of many other tips..... I really do love my bag. It's a perfect size for me. I have just one in diapers, but it seems like I'm forever toting around extras such as sippies, shoes, stuffed animals, etc... so the extra space is greatly appreciated
