ROGERO 4.21 [Sc-36l Hermes] HELP

Hi

trying to put 1tb hdd in ps3 slim with above cfw on it. Can anyone help.

Have looked at guides for downgrading Rogero followed them but no joy keep getting asked for update of 4.25 or later. I want to be able to down grade to 3.55 install hdd then back to 4.21 cfw. Please help. I HAVE FOLLOWED GUIDES POSTED ELSEWHERE ABOUT DOWNGRADING BUT I DONT GET ANYWHERE.

I dont know if they are for phat or slim or if pkg`s are dodgy need help

Thanks

PS if anyone who knows how to do this is in North London that would be great;)