Higher upstream speed on ADSL2 - what happens if you force ADSL1

[#1]

This occurred to me because of a reported problem where a customer has been put onto ADSL2 with uncapped upstream and is having disconnection problems
What happens if he forces ADSL1 on the router - does he keep the higher upstream speed or does everything fall over

[#2]

You can have uncapped upstream on ADSL1 as long as it's 21CN, so I'm not sure that it would affect it

[#3]

I didn't know that - so why don't you offer it