How to downgrade RSU or can we do cross version flashing?

[myO2]

hi all,
anyone know how to downgrade radio stack (RSU)?
My O2 XDA is PW10A 900/1800mhz, ROM is A.30.09 ENG, RSU 4.21.00.
The current RSU seems unstable and many said older version more stable (4.01).
Where can i download the old version?
Thanks.

[Biso007]

Try Yorch.net ... but be careful as there are many sad stories here about people tried RSU flashing while having this 4.21

[myO2]

thanks for the help biso,
which RSU suitable for my PW10A 900/1800mhz?
t-mobile 6.24.00 or at&t A20.10?

thanks.

[Rudegar]

if you want 900/1800 then you cant use an US radio stack

on yorch the tmobile is called us tmobile
and i think that AT&A are also only in US
if you use a us radiostack you can only use 900Mhz

[myO2]

so..what's the best RSU for 900/1800 and where can I download it?

thanks.

[Rudegar]

well i would suppose that o2 would have one

[myO2]

O2 site has only the latest version. i'm looking for the older version, where can i find it?

thanks.

[myO2]

just the idea...
is cross version flashing possible?
e.g. we flash 4.21.00 (o2) to 6.25.00 (t-mobile) then flash it to 4.16.00 (o2)?
i remembered i flash to 6.25.00 once and reflash it to 4.21.00, but cant remember the steps.

any suggestion?
thanks.