Just returned from 3 weeks in France and Spain. I have 4 products: backpacks, waistpacks, messenger bags from PacSafe. This is a wonderful size, finally one that can fit my passport, wallet, iphone. Lightweight, with the security features standard on PacSafe products. I can fit a light goretex rainjacket inside, ipad Mini, water bottle inside or attached to outside loop. Compact rangefinder camera can also fit.
My ONLY suggestion with your sling/crossbody/waist pack products is to provide a slightly longer strap so that it does not sit so high on my chest when in crossbody mode (which is essential now in Paris, with Olympics drawing a flood of pickpockets to the Metro). I am 6'2", 46 chest, 190 lbs (athletic build, not obese) and the sling sits a bit high on my chest. 3-4 additional inches to a strap would solve problem, or, provide a modular add-on strap that slides into extend the locking slide attachment, PLEASE! I would gladly pay for this additional accessory innovation.