Richard. I have just bought an Olympus 50mm f1.8 lens on ebay for £2.75 so I will be trying the same conversion as you have done.
This lens has a faulty aperture mechanism so I'm not going to feel guilty about destroying a perfectly good lens.
I will wait until I get the lens and take it apart but if you don't mind, I may have some questions regarding the way you modified it - especially making a new slot.
My Minolta conversion needs an external pin and slider bracket assembly to prevent it from turning so your Olympus method would look neater.