Might be more trouble than it's worth, but you can "strap" the phono outputs if your system doesn't offer a mono switch. With a mono switch strapping is then done in the pre-amp. What I do is run two turntables in two different systems. The dedicated mono unit is 1, an e-bay and then overhauled Pioneer 1150. The Pioneer runs the Grado MC+ (there is a new upgrade MC+), the other, 2, is a Pro-Ject Debut Carbon DC with a Audio Technica MC cartridge through the P-J S box, that cart has since been obsoleted and supplanted. You can play mono with a stereo cartridge, each side of the cart will feed "stereo" outputs to your system. I have noticed the effect you mention when playing a Shibata stylus. Do not play your stereo records with a mono cart. For Jazz and Classical I prefer Mono, it gives a more "sitting in the front row" experience for me, not to mention going back to the days of mono systems.
Mono record sounds like stereo
So I have been playing stereo records for 40 years. I’ve recently acquired some Verve Japanese reissues. Listening to Metronome All stars tonight and there is clearly separation. I hear horns predominantly on the left and xylophone and drums on the right. This is on an Ortofon SPU synergy stereo cartridge. Is this normal ? I’m sorry. I’m new to Mono. I bought about 50 verve and Blue notes last week and got some monos on accident. My system is balanced and the room has extensive treatment so I’m lost !