D5500 - Motorized

I recently got a D5500 with the motorized head elevation and focusing. I mounted an MG-500 head to it. The head elevation motor seems a little underpowered for the MG-500 head. It will elevate just fine, but when you stop the motor, the head "sinks" a little - like it can't hold the weight. Seems to me that the MG-500 head is a little lighter than the CLS Dichroic head I had on my previous, non-motorized D5500. It's not a huge problem - I can lock the head as I release the motor - but I was just wondering what the experiences of others might be.

Thanks

Bob H