Defender TD5 15P Rocker Shaft - Upgrade from the 10p?

Hi,

With all the issues I had with the adjuster screws recently I bought another rocker shaft. It's for a 15p engine (mines a 10p) but I understand the 15p version is an upgrade for the 10p. Has anyone found this to be anything other than correct?

Question is, is the 'upgrade' worth the trouble of removing the old and refitting the new?

Thanks!

The 15p is indeed a modification, unable to evidence this (I can't find where I had it from) but the 15p rocker is larger in diameter so will not be a straight swap.