#1 looks are subjective.
#2. a 2-5 inch stretch wont kill handling, but it can change depending on how much u stretch it. ive seen busas and zx14's tearing up the canyons-stock wb is about 57-58 inches for them. average 600 is about 54in wb. add 4inches and you're at stock wb for a busa. if for some reason you cant ride it, you dont need to be on a bike.
#3 imo anything over 6inches doesnt look that great without changing the bodywork. if you actually were to do it, to look nice you need to rework your swingarm, or buy a new custom 1. the extentions look tacky. thats alot of work/cash for 2-3inches, but it would look good. alotta bikes have that "pushed in" look. some like it, some dont. personally i think honda's new 1000 looks the best from the swingarm pivot back, because it has the illusion (the wheel is back alil further than the end of the tail) of being stretched.
#4 i highly doubt the majority (if any-maybe 1 besides me) of the posters in this thread have ridden a stretched bike anyway. thats why u got mostly b.s. answers.
i gave you some info, but cant answer your question because it all depends mostly on how much you stretch it, but also if you also lower it, go to a wider tire, and if you adjust the suspension according to what you did.
Whew that was close....I had this long angry post written and everything...
Anyway,there are a ton of forums on the web that support stretched sportbikes. I'm sure you can find a plethora of information on them. I've owned a 'Busa and I've ridden several stretched bikes. The 'Busa was designed around a longer wheelbase. The 'Busa swingarm is the same length as a GSXR,I believe. The rider sits further back on the bike. The rake and trail are different. The CG is different. Where the swingarm pivots. The angle of the shock and the link angle and location is different. Most have the forks "strapped" down which shortens suspension travel only in the front. Making a 600 have the same wheel base,by lengthening the swingarm,will not cause it to handle the same as a 'Busa. Anymore than modifying the steering head to lenthen the wheelbase.
Since I "BS'd" the answer before...
Likes: looks cool,women love them,launch like crazy!
Dislikes: Lessened cornering clearance,typically harsher ride,say goodbye to wheelies(more or less).
I guess I'm just tired of looking at them. My buddy works at "Ron Ayers" and showed me a bike. GSXR600(white),brand new,0 miles. Stretched swingarm,chrome everything,lowered,you name it. It looked cool but
I hope that this was better.