I think the more relevant comparison would be to the
Langes Messer
weight: 1.8
difficulty: 13
speed rating: 98
weapon length: 92
thrust damage: 23 pierce
swing damage: 33 cut
slots: 1
Secondary Mode (2h)
You'll note in exchange for being 1 slot and having 2h mode, it is actually a good bit shorter than the bastard/longsword, and slower / little bit shorter than the katana. I honestly think the slots are fairly balanced currently. Though the fact that the Langes is the #1 sidearm of choice probably means it should be balanced in comparison to other sidearms.