The DL103 should be fine in the Jelco. However, it is important to measure the resonance frequency with a test record as there is a large amount of variability. You also want to make sure you are down by 8 Hz for the best bass.
Denon DL-103D compatibility with Jelco TS550L arm
Unlike most of the DL 103 series cartridges, the D and S variants have elliptical stylus and compliances of 12 cu and 8 cu respectively. This is a much higher compliance than the spherical stylus versions with a compliance of 5cu. Denon's cartridges compliance is spec'd at 100 HZ rather than the more typical rating at 10 Hz that most western companies spec their compliances at, so I'm finding it difficult to determine compatibility with tone arms.
The Jelco arm matches up OK with the Zu Audio DL 103R that I have, but I'm thinking it is probably too heavy to use with the DL 103D.
The Jelco arm is mated with DP80 in a custom plinth. I also have a refurbished DP59L with servo tracer arm, that might work better with the 103D or S version of 103.
Any thoughts and advice would be greatly appreciated.
Regards,
Keith