is this legal in florida side plates ?

http://www.ebay.com/itm/Kawasaki-Ninja-300-License-Plate-Holder-bracket-Side-mount-Rolled-/261260968631?pt=Motorcycles_Parts_Accessories&hash=item3cd45e02b7&vxp=mtr

Looks like a good left hand turn would grind off half of your plate.
Most states you can get away with those during the day. You need it to be lighted for night riding. Pretty sure it wouldn't pass safety inspection without the light here.

Seems like vertical mounting can be legal in FL; it varies state by state. It would require a plate light.

(quoted from here (http://www.leg.state.fl.us/statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0300-0399/0316/Sections/0316.2085.html))

(3) The license tag of a motorcycle or moped must be permanently affixed to the vehicle and remain clearly visible from the rear at all times. Any deliberate act to conceal or obscure the legibility of the license tag of a motorcycle is prohibited. The license tag of a motorcycle or moped may be affixed horizontally to the ground so that the numbers and letters read from left to right. Alternatively, a license tag for a motorcycle or moped for which the numbers and letters read from top to bottom may be affixed perpendicularly to the ground. Notwithstanding the authorization to affix the license tag of a motorcycle or moped perpendicularly to the ground, the owner or operator of a motorcycle or moped shall pay any required toll pursuant to s. 316.1001 by whatever means available.

...for which the numbers and letters read from top to bottom...

That says to me that a standard left-to-right plate wouldn't be legal in that position, only a top-to-bottom tag.

From what I've seen, those curved plate mounts near the rear hub are popular with the choppers and such. MI is pretty lax about small stuff like this, so it may not be a good comparison, but I'd think that you'd be ok with it as long as it was fairly visible to a cop behind you. The spirit of the law is to ensure that your license plate is legible, so as long as you're not going out of your way to make it illegible, I think you'd be ok (around here at least).

One other effect of that style mount is that it can make it a lot harder for random cameras to see your plate. I've heard of people in areas where they have lots of drug or border surveillance preferring these mounts for privacy reasons. I'm not condoning or encouraging illegal behavior, but I don't condone unconstitutional government monitoring either.

If you're getting a vertical mounted license plate with letters in the correct orientation because while legal it subverts automatic camera recognition systems, do you not think that would draw more attention from the police whom as you've already mentioned will be aware that people use this is a means of evading being caught speeding etc and subject you to more pullovers as a potentially suspicious vehicle?

it seems like vertical plates are only legal where helmets aren't required

I rode a CBR600RR for a year that had a vertical license plate. I don't even think there was a light. Never got any attention from the police. I did buy the bike used...I don't think I'd do that mod myself.

No