Replay Gain: A how to informational

@miikerman wrote:
Yet further reason why I like MP3Gain–works every time!

How do you get MP3Gain to work. I tried it and first of all it writes Ape tags which the Clip+ doesn’t read properly (if at all), and secondly it does the same as Foobar2000 on positive values, and writes a “+” at the beginning of the ReplayGain value, and the Clip+ subtracts 50 from this value, so a RG value of +2.0 becomes -48.  What am I missing?