Domke DSLR Camera Insert (Gray/Green)

would it work with f3?

From personal experience, the dividers add very little to the rigidity of the bag, but make it very lightweight and easy to travel with. There is adequate protection for most cameras and lenses as long as I am not too rough with my gear. Going along with some of the other answers to this question, the underneath/external side of the Domke dividers have pockets where the foam is inserted. You might want to consider adding firmer/more rigid material (such as cardboard) on top of the foam just to add even more rigidity.

No, too big.

Quality of Velcro is alright only things is use different kind of bag instead of messenger bag

This insert has dimensions of 6.25 x 11.5 x 8.0 , while the Domke F-3x has interior dimensions of 5.5 x 9 x 8.5 . Based on this information the insert is larger than the interior of the bag.

Yes, it will fit. The Domke 720-250D Digital SLR Camera Insert is designed to fit any Domke bag that has a standard 4-compartment insert.

No, the insert is too large. I have used it in the original F2 bag and the J2 bag.

Yes. The insert is about 6 x7 , and the length of the F1X is about 17 . It is not necessary to remove the foam padding in order to fit this combination into your bag. Note that there are a number of options and combinations available to suit your needs. That is an advantage of this system.