I don't buy that. I have Steeda HD mounts which are superior in design... the clunk comes back to you after the spring sets in.
I feel your thinking/theory is sound, however,,,,,evidently the Steeda HD mounts are NOT superior to the upgraded Ford mount or you wouldn't be hearing any thunking at all. I would agree that the Steeda's are superior, heck my ***** are superior to the original Ford strut mounts ;-D.
However, you are a lot closer to the cure than you realize in that your idea that a different kind of material may be the answer. You're really not wrong about the cure materially speaking but you are incorrect regarding which parts need correcting or enhancement.
You will be wasting your time taking the front end apart and installing those hoses over the spring ends for fitment into the spring seats. How do you know they will even stuff themselves into the spring seat after you install the thicker sleves?
I bet you end up having a fitment problem if not destroying the sleves's after going over a few bumps even if you manage to stuff the spring ends into the spring seats.
Ford's new upgraded mounts CURE the thunking issue, period, end of story. That's a fact.
Here is what bascho, who works at Ford and actually designed the replacement bracket/strut mount, says in post 1367, page 69.
The new mount will look identical to your original except the mounting studs a few mm's longer. The real change was tothe compound of the rubber used in the mount. The "chuckle" or "loose-lumbar" (as is was called in the concern write-up) was attributed to the "radial" and a"axial" rates on the mount. The new rubber compound corrects this issue and thus corrects the"loose-lumbar" noise from the front suspension. I've compared the test graphs of the two mounts and there are drastic improvements to both the static radial and static axial rates for the new mount.
Ask your local parts person to enter 8R3Z-18183-B"
I'm not saying your repair couldn't work. I feel however you are wasting time and money. I have heard of others installing the Steeda's and getting rid of the thunk and I have heard just the opposite. At any rate, by replacing the strut mounts with after market components, it's a crap shoot.
If you replace the upper mounts with the above part number, you'll be good to go. That is unless you want the ability to adjust wheel angles to the road. Then yeah, you're probably gonna be stuck with the thunking noise.
Best of luck in any case. I know how frustrating that noise is and I also know what a joyful heavenly feeling it is to have it cured once and for all! ;-)