Defender 90 rear prop

Hoping someone can answer a query for me. I've been suffering from a bit of vibration on my 90 and have finally tracked it down (I hope) to my rear prop. I had play in both u/j's on said prop so replaced, put prop back on and still vibration, only occurs under acceleration at precisely 40mph and stops at 46/47mph. So went over other things thought it could be, wheel balance, bushes, bolts, bearings etc. eventually clicked I had no vibration when rear prop was off, so this evening I've removed rear prop to find no balance weights on it but a square patch where I presume 1 used to be. My question is, I have rear prop off until I can sort it but when driving without rear prop the landy is pulling like a c$%t to the right when accelerating, is this the norm? It tracks perfect and brakes dead straight with both props on.

The patch is the balance weight.

I'm a dumb ass, obviously it will pull, just worked it out. Wieght is missing, two jubilee clips with screws where wieght was has sorted it for now, no vibrations.