Speedometer is off. Correction via SManager?

[ITR 1102]

My speedometer is off by about 10 miles per hour at 80 MPH.
It may just be the speed sensor as every now and then it will just go crazy and then settle down, but I'm not sure. The faster I am going, the more it is off.

Is there any way to have Hondata correct this? I have confirmed with other cars and GPS that my speedometer is infact inaccurate.

The speed sensor is OEM, but the speed gear is the ATS / Carbonetic since I have their Carbon LSD installed.

Is there any way I can create an offset in SManager to correct my speed by my RPM? The tach RPM is very accurate with the computer (until close to redline). The speedometer reads exactly what is shown in SManager -I just know this value to be wrong.
Tire size is 205 50 15, but the problem exists with my stock 195 55 15's as well

[Hondata]

The speed signal goes from the speed sensor to both the ECU and dash. The ECU cannot change the signal. Look for speed signal converters online.

[CarlosSpiceyWiener]

So I'm digging this up because in the new version we now have a tab that reads:

ECU Speed and offers you a Speed Sensor Correction in %

[Spunkster]

this is only for datalogging. The ECU does not send a speed signal to the dash.