My head is spinning!
A little knowledge is dangerous, so am I.
Have used a variety of cartridges for CD-4. PSX-6 SONY DD S-arm. Most experience w/AT & Ortofon. Have experimented with many cartridges w/o buying them. Perks of working for a dealer.
Prior to going AT CD-4/4 DD5, I had Shure M91ED. Used Pioneer PLA-35 w/Shure and AT14sa/4 DD5. Elliptical for CD-4?
I use Shibata for CD-4, Fineline for 2ch & Stanton conical for 78's.
Used phono cart, no. What has the stylus been through? Shibata has squared back end. That breaks or wears unevenly, you could trash 🗑 those CD-4's.
Is it a nude stylus? Bonded can break away, depending on the bonding method. A 50 year old (ab)used cartridge isn't anything I'd use to play my cherished vinyl.
Fineline, etc stylii are rounded and will work for CD-4, kind-of. I prefer these designs for 2ch/matrix playback.
Tracking force: more LP'S are damaged by too little than from too much. Forget about taping
to add force!
Slightly warped records are especially affected by low tracking force.
Mismatched arm/cart, inadequate setup disc, incompatible MC preamp/transformer, improper cartridge alignment and a million other issues can affect CD-4.
Ortofon MC can and will work... AT, Precept are simpler, lower cost MM solutions. MCA-76 works. T-20 sounds smoother w/cleaner highs on 2ch & matrix. Mixed results at best for CD-4 on T-20. 90% of my total vinyl listening has been Ortofon MC for 45 years.
No surprise, EVERYTHING needs to be right in setting up CD-4, including what cartridge works best with each pre-preamp/transformer, tonearm, etc. Don't forget about capacitance of cables.
Like an expensive sports car, it's finicky. Still, it's worth it. When you get it right, it stays right, at least until you
fiddle with it. Sandpaper, occasionally but rare.
If I ever grow up, I might get that VPI Scout I've been drooling over!