HELP! Fitting Steel Diff LA201

[redsdreads]

HI

I am changing over to a new chassis and thought I'd upgrade the rear diff with the Kyosho Genuine Steel Diff Shaft Set.
Unfortunately the washers that go against the bearings do not fit the steel set....they are like a normal washer but with two opposite flat sides.
Do I just go ahead and fit these? It looks like the one on the longer metal part will just flap about!

Has anyone fitted this part and can explain if I need to get some new washers or if I'm just being a dunce.

Quick reply would be appreciated as I wanna get my new Losi motor in an rag this baby!