IPhone :: My JB Phone Has A Hardware Issue Can I Back-rev A 4.0.2 Phone To 4.0.1

I discovered over the weekend that the speaker on my iphone is broken and I want to replace it with a new phone. (This includes no audio notifications for phone, messages or emails). My phone has been JB for over a month, and, as part of the process for determining if the JB was the cause of my speaker not working, I reverted my phone back to a pre-JB state on 4.0.1 (with a lot of assistance from people on this board!). I have 4.0.1 firmware and Cydia has my SHSH info.

Here is the question: can I back-rev a 4.0.2 phone to 4.0.1 given the above information (using Tinyumbrella etc) or must I wait for the 4.1 JB?