Exakta Varex VX and Tamron Lenses

I lucked into a couple of nice Tamron lenses for very little money, and to make it better, I found a Tamron Adaptall for Topcon. Since Topcon and Exakta used the same mount, I thought this would work.
When I tried to fit the lens onto the camera body, the lens release lever got in the way. It has a little knob on its end which prevents the Topcon adapter from sitting flush into the opening.
Has anyone had experience with this problem? Can the knob be removed from the end of the lens release lever?

IIRC, they had to be mounted upside down, one to the other.