hey, that's my front wheel.

and max's yellow fender.
i don't believe the fender will cause the problem you describe. with the gearing 85-90mph tops been there, done that, got the tee shirt. didn't feel like it was a problem.. it's the gvw that's a problem at high speed.
wanna go faster get a different bike.

but never give up your thumper, there is nothing like it out there
now if you want a sleeker look that's a whole nother story.
fyi max does post here so he may well chime in on the subject. he does have a sweet looking bagger and will be swapping out his rear fender for one like the front.
and believe me if max gives advise TAKE IT. he knows of what he speaks.
I on the other hand only knows of what i have actually done. like push starting, yes it can be done. starting from a stop with no clutch, wild ride but doable.
sliding it down the road on the rear fender. It's called a high ho silver away. dont try that at home boy's and girls. 8)
enjoy buy fuel it's the accessory the bike loves the most. SINGLES RULE, HARLEY'S DROOL.