As long as we are on the subject of frustrations with Marble sights, maybe someone can give me advice on mine.

The rifle came with a Marble tang sight, but no stem. Bass Pro said they would send me a stem, which they did, but it was for a Lyman sight. I then ordered a stem from Mike in the UP, and I cannot get the body open far enough to get the stem in. Then bought another stem, which the dealer said had been on a sight that he had parted out, so it should go in just fine. Still will not fit. The stem is round, with a small enlarged threaded section on two sides. The hole and slots on the sight body do not appear to be large enough to allow the stem to enter. What am I doing wrong?