Some other options:
1. Replace main Jelco with the TK-850. Drop-in replacement. It is a substantial improvement soundwise and will elevate your perception of how good your rig is. George Merrill has the best price.
2. Put your 12" 750 Jelco on a pod at back of table behind plinth and using a light wood headshell, try the MC10 on it.
3. As 2 above but use lower compliance cartridges instead like a Decca.
4. Sell 750 and use an off-board pod for other 12" arms.
5. Drill bamboo for low mass 9" arm of your choice.