I think he means the RO cape is a bit short, as I've heard that.
That problem gets solved by putting the RO cape on the ANH Vader because the ANH Vader is slightly shorter than the RO Vader (chest armor/shoulder bells may also play a roll in raising the cape in back).
Again, this is ANH Vader so he should be duller and duskier -- you want hi-gloss Vader, wait for ESB/ROTJ.
The ANH version comes with the duller dome, and the better, flatter, thicker body suit. Get those RO gloves and place the belt boxes and chest box in the proper positions, and drybrush the gloss out of the chest armor, and you have a perfect ANH Vader... with electronics if you ever want to hear Vader's voice and a light-up saber (although there is the glove issue here).
If you missed ANH Vader... then getting this new Vader is a no-brainer.