Why are many people recommending using the 180/55-17 rear tire to quicken the turn-in?  All you have to do is lower the forks in the triple clamps by about 1/8-1/4 inch.  Does the same thing and doesn't affect the speedo.

I don't think there's room to lower the forks in the triple clamps because of how the handlebars basically bolt on over the top of them.  Plus, a 180/55 is probably going to be very close to the same height as the 190/50 so it's not going to raise or lower the rear much or affect the speedo much.  Most people are talking about a 190/50 vs a 190/55.  The 190/55 IS taller than the stock tire.  So I'm sure raising the rear is part of the handling difference.  However, the tire also has a "sharper" profile which makes it fall into corners quicker.  And the affect on the speedo is a positive one because it corrects for almost all of the factory speedo error and makes it more accurate.

If I rise the bike any more my toes won't even touch the ground

I don't think there's room to lower the forks in the triple clamps because of how the handlebars basically bolt on over the top of them.  Plus, a 180/55 is probably going to be very close to the same height as the 190/50 so it's not going to raise or lower the rear much or affect the speedo much.  Most people are talking about a 190/50 vs a 190/55.  The 190/55 IS taller than the stock tire.  So I'm sure raising the rear is part of the handling difference.  However, the tire also has a "sharper" profile which makes it fall into corners quicker.  And the affect on the speedo is a positive one because it corrects for almost all of the factory speedo error and makes it more accurate.

There is over 1 full inch of room before the top of the forks would hit the handlebars (more with risers)  I've lowered mine and I've checked the clearance.  All bikes are designed to move the forks up and down slightly in the clamps or they would just mount them solid to the clamps.

This also puts your feet 1/4 inch closer to the ground if that matters....

Wouldn't mounting a 180 on a 6 inch rim flatten the profile?  They are intended for 5.5 inch rims.  I know track riders that mount 190's on 5.5 inch rims on their 600's and 750's for a wider contact patch at a high lean, but I've never seen the converse.