Are you sure? I would have thought that [Client] mode meant you were acting as a traditional 0.4 Gnutella servent. I've been an Ultrapeer so long I don't remember, but I thought the new Limewire started out saying [Leaf]. If you select the option for "Disable Ultrapeer", then I thought you would always be in [Client] mode but that there was a bug that prevented you from connecting to more than one other host, i.e. you'd still act like a leaf.

Anyway, there's a new version that changes a lot of the Ultrapeer/Leaf "tuning" so it's going to be moot soon.