When I first read this I thought no absolutely not but after further review of these pumps I'm on the fence and think contacting Jason Kim the president of AquaC would be the best reference.
Here is the break down...
The mag24 has less flow 2400 gph but a much higher max head height of 18ft.
The fluval sp6 has more flow 3434 gph and lower max head height of 13ft.
But, @11ft the mag24 and sp6 have 950 and 1003 gph, respectively. So, the pumps are very comparable in that sense.
The fluval almost uses half the amount of energy, 265 vs 135 watts, which is very appealing. Mags are not the most efficient but the extra wattage certainly contributes to the difference of max head height. The primary concern with the sp6 is that it falls off so fast. It goes from 1003gph @ 11ft to 0gph @ 13ft, in just 2 feet it losses 1000gph and this may cripple the pumps ability to drive the skimmer properly. The mag24 has a much more gradual decline in flow which is probably why in so many cases that mags are the preferred pump for these skimmers.
It's been well documented that these skimmers perform better with pressure rated pumps and that max flow does not necessarily increase the performance, the mag is probably the best option for performance. But again Jason would know the answer. He would be able to analyze the pumps and give you the best recommendation.
If you are looking for a submersible pump option outside of the mag24 then the Sicce Syncra High Flow or HF series might be the best bet. The power curve/max head height on the HF pump is respectable and should be comparable to the performance of the mag with much less energy consumption.
TLDR: Contact AquaC about Mag24 vs SP6 and consider a Sicce Syncra HF 10.0 or 12.0.