Attaching a fifi hook?

I have thus far only done aid to get up climbs to then practice on top-rope, so I am not setting out for a big wall or anything like that and am not very experienced in this area. But I have a BD fifi hook and I want to replace that thin little piece of webbing that comes with the hook.
Ideally I would like to do it with either a short section of dynamic rope (10mm) or a dyneema sling (I have both of these that I have retired from holding more than body weight, but am completely confident they would hold body weight still, so I wouldn't need to buy anything else). Having the fifi adjustable would be nice, but I would also like to be able to have it fairly short. Ideas? If there isn't a very good way of doing it with either of these materials then I'll suck it up and spend the few dollars on some more cord.

Why do you want to replace the webbing that comes with the hook? The stock webbing is adequate for what the fifi hook is designed for. Replacing it with 10mm rope is going to add a ridiculous amount of bulk in an area that already has too much crap (e.g. lead line, two daisy chains, fifi).

If you want an adjustable fifi you can get the Yates adjustable daisies. They are not "fifi" hooks, but they can be used in their place. That's what I use on walls. Likewise, Cassin makes a dual fifi that has two hooks on one sling, one short and one long.

That's been my issue with why I haven't just gone straight for the dynamic rope, it is very bulky. But again I happen to have it on hand. I want to replace the webbing on it because I feel like it will need replaced relatively soon, this is just based off how thin it is so it could be more durable than I expect. Until/if I get into real aid (I have yet to go out with the intent on aiding) I guess I'll just see how long that webbing lasts and replace it with cord once it starts to get frayed. I could probably get away with just using a biner to clip it directly to my belay loop (so no webbing or cord, just belay loop>biner>fifi) as well (again, this is just for intermittent use for now).

The webbing that comes with the fifi will last a long time for "intermittent use".

Climbers have climbed dozens of walls on El Cap without ever replacing their fifi and by your own admissions you're not an aid climber. Unless there is some specific damage you need to repair, I wouldent worry about it. If you really want to replace the webbing, use 5/8" webbing and have a professional sew it together so you wont have a knot getting hung up on stuff.