I thought long and hard and took your advice and tried it, purchased a MP10 and it works fine on a 1/2 inch glass 120 gallon tank.
I dont know the tank manufacturer but its either All Glass or Oceanic.
The MP10 arrived yesterday, I installed it at some point before 7pm and tested it.
The pump wet side does not spin on full speed.
The pump holds firmly and I am able to move the wet side by manuvering the dry side, the wet side does not break loose.
I tested the magnet strenght over night by leaving the pump on full speed and without the glue on safety zip ties, the pump held, woke up and the pump is still on the fish tank.
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I cannot say that the pump will never fall off hence why the safety zip ties will be used.
Conclusion is the Mp10 works fine on my 1/2 inch thick glass fish tank. People wanting the features of a Vortech can probably try the MP10 instead of buying the MP40 may not get used at past 50% power.
In researching it I did find that glass lead may be a factor on whether or not the MP10 magnets will be sufficient to hold reliably on 1/2 inch glass, like I said, I have a standard 1/2 inch glass 120 gallon 48x24x24 fish tank and the MP10 works.
I purchased my MP10 brand new from a vendor instead of paying $200 for a used out of warranty MP10. I try to get around to registering this new pump sometime this upcoming week.
IMO if your running a mostly softie/zoo tank the returns and 2 MP10's would suffice if offset from each other. The biggest thing is your going to be running them at 80% to get the same flow as the 40's at roughly 30%. And you'll need a dab of silicone for them to hold.