I was playing with my new HM-750 the other day to see if there were any major differences between it and my HM700 (other than the 720x480 SD mode, there are none).
I plugged in an SDHC card and noticed, to my surprise, that it said I had 160 min. of record time available.
I had just pulled this same card from my 700 where it said I had 115 min.
The card was freshly formatted and the camera setups were identical.
All I can surmise is that the difference is due to the SD record mode even though the cameras were set to MP4 1440x1080 60i.

Hi Mike,
the answer is simple. You HM750 is set to a different record mode than your HM700. 1440x1080/60i can be set to 35Mbit/s (HQ-mode) and to 25Mbit/s. With 25Mbit/s you will get 160 minutes and with 35Mbit/s you will get 115 minutes.
Joachim

Thanks Joachim.
I'm positive that I set both cameras identically but I'll confirm that tomorrow.

Thanks again Joachim. Your suggestion was indeed the answer.
I need to spend (a lot) more time reading the manual.