Thanks folks for all the info and I realize now I should've added some extra - I'm on Poser 4.03 (not Pro Pack) on a Windows system. So, while the left images are .png, P4 does not create those by default and cannot (will not?) read them if they are just pasted in to replace the normally generated .rsr files. sigh I already tried it...
Anyhoo - I'm gonna give that RSRConverter a go to see how I like it - hopefully it's simple......like me ;)