I bought the F6 with a case, the K-Tek KSF6, which seemed a perfect combo. This case is brilliant, really well made. Unfortunately, though, I've come to hate it. Let's see why, and what I did about it.
There are many good things about this case. The rigid frame provides great protection; and the recorder locks securely into place, which is fantastic — it's not moving whatever happens. But the one place it doesn't provide protection is the front panel, so when I chuck it in a pack to take home, the screen can get scratched and the knobs ripped off. The rain cover K-Tek released after the fact looks, feels and works like a bodge. I'm sure this bag is fantastic for booming a mic, but for transport, it's pretty hopeless.
I find the strap particularly annoying. Again, it might be great for using the recorder on your waist, but it's absurdly long — it goes nearly twice around me, and I'm not a ballerina. The worst thing is it's not removable; so if you're not actually wearing the recorder, you're stuck with it dragging on the ground everywhere you go, tripping you up, and so on. This is what I find particularly frustrating.
I would happily cut the strap off, but there's no alternative. There are no D-rings on the bag, and no provision for fitting any; so no way to fit a shoulder strap, or hang it from a tripod, or anything like that.
So here's my solution. The bag is a FlyLeaf; sorry, I don't know what model, or when I got it, or what for. But I got a strip of 75mm (3 inch) hook fastener, sold for fastening wires down to carpet, and cut a strip to thread through the rails of the recorder; this fastens it to the fuzzy back wall of the bag, and holds it in place pretty firmly.
The bag has D-rings, to take a shoulder strap; and a very nice, padded waist belt, which you can remove.
I have space to permanently connect a pair of low-profile XLR plugs on a Y cable for my stereo mic setups; and a right-angled headphone cable leads into the compartment on the right, where my headphones just cram in.
I haven't had a chance to do much field testing yet, but this feels snug, secure, usable, and packable. I'm going to have to remove the recorder to change batteries, or the SD card, but that's not too bad. With an XLR Y-cable permanently connected on the left, and the headphones permanently plugged in, I can connect the mics and get recording pretty quickly.