Whoever told you about different bar thickness doesn't know what they
are talking about
Besides , what are the odds of you finding the length you want off the shelf ?
Manufacturers don't make that many different lengths .
They purposely make them on the long side so consumers can cut them
to their personal preferences .
In the area of the grip (only spot you would be cutting) it is all the same
whether it is an aluminum , carbon or 31.8 bar .
Don't make cutting your bars sound more difficult then it is .
If you can cut a raw carrot , you can cut your handlebars .
Measure twice , cut once .
Some bars actually have measuring marks on them so use them for
The ideal cutting tool is a plumbers pipe cutter .
Only use top end ones as I have found the cheaper ones fail to hold a straight
line while cutting .
I just use a hack saw with fine cutting blade (high tooth count) .
Don't worry about the end cut being 100% straight/flat as you can always
level it out with a few passes with a file .
You don't have to cut the end of your grips off to get them off either .
On the opposite end of the grip (that faces the brakes/shifter) , pry the
end up with a narrow slotted screwdriver . Leave it in there and then
spray in some WD 40 (get the straw in as deep as you can ) and twist
a couple of times and pull it off .
Before re-install of grip , clean the remaining lubricant off bar and inside of grip .
Put everything back on and take the bike for a ride or two before deciding if you
like it or want to remove more .
Now get to work