ReadyNAS Duo v2

I have a ReadyNAS Duo v2 that was used to store Unitrends cold backups through a nfs share. Somewhere along the line the nfs version has changed to nfs3 which isn't supported by Unitrends. It has worked before so I expect there has to be a way to change the version back to nfs2. I tried grabbing the earliest version of firmware available from Netgear but no dice. Looking for some ideas or helpful information. Not sure if my searches are specific enough or what, but I haven't found anything online