Desire to underscan Horizontal

[Opcom]

I have a need to greatly underscan a tube type monitor chassis. The reason for it is because I have replaced the 110 degree 8" 8HP4 rectangular tube with a 10" 55 degree round tube, a 10SP4. I have not changed the yoke yet. Maybe it will be done but it is worth it to try without it.

I've tried going to a lower tap on the H out. transformer but it's not working out too well. I noticed in another thread about a color set where it was suggested that an unwanted or excessive overscan could be reduced by changing a tap on the yoke. The function of this change merely put a 560pF capacitor in series with the windings.

On my chassis, a Conrac CNB-8, there is a width adjustment but I am at the end. I have tried putting a small inductance in series with the H winding and then to correct back down the overall inductance necessary for the circuit tuning, placed an inductor across the H yoke winding.

I have not tried a capacitance in series yet. Has anyone had experience adjusting tube set widths to unusually narrow settings or with using a tube having a lesser deflection requirement?