Mini_k,
I can't answer your "lowering question" but 30mpg sounds pretty poor milage to me. I ride very briskly on my Sprint every weekend and I get 50mpg.
As for mods I have the following on my bike;
Triumph rear hugger,
Radguard oil & radiator protector
Triumph Gel seat
Ventura Packrack
Triumph Datatool S3 alarm system
Triumph Daytona rear hub nut cover
Triumph SS race can
Triumph CF race can (not at the same time

)
Photos in my album of all the bits and an assortment of different tyres also.
Davem