Cavity/Jig Fixture

Hello all,

I'm trying to make a 'simple' fixture jig for this part. I have tried with both cavity and combine-subtract.

Both methods leave the same results, an overcut between the cavity void and the top surface of the block.

What im trying to achieve, is the full profile of my part, hollowed into the block. So the part can be sat in the jig.

Any help is greatly appreciated. I can send the part files if required.

Thank you in advance