Converting RCOs for 3.71
To answer your first question, yes you can use RCOs on 3.71
The only RCO that you will have a problem with is topmenu_icon.rco
For some reason, that is the only RCO that does not support compression of any type
All other RCOs can be treated normally
So lets tackle that nasty topmenu_icon.rco first.
You need a special version of the RCOeditor for 3.71
Zinga, as always, came through for us and released a version that will not compress image data.
First step is to open the older version of the RCO using the hacked version of the RCO editor
Choose the "Extract all option" and choose a folder to save the extracted icons.
Once you've done that, open a decompressed topmenu_icon.rco for 3.71
Now choose the Replace Multiple option and find the folder with your previously extracted icons.
Now you have just made your theme compatible with 3.71 :)
As for the other RCOs, you can use the regular version of the RCOeditor with decompressed 3.71 RCOs
Flash space has always been a problem for flash users. And since the topmenu HAS to be decompressed it can get rather large.
You can compress any other RCOs besides the topmenu_icon.rco to save space
This can be achieved by using Resurssiklunssi v0.3.
You will need a decrypted sysmem.prx from an older firmware such as 3.40. You can use the new PSAR dumper to dump everything decrypted.