As I figure it, maybe the best way to plan my first purposed bag, a smaller bag sized like a fatboy, would be to lay out all or most of the stuff I hoped to carry for (for example) hunting walks in the bush and trails. Measure if needed for length of longer pieces, bulk etc. And begin to look for a bag to meet the need. Or, buy a bag the size I want to limit to for the purpose and then fill as best I can. Or is there a Better Way? What do you guys think?