There is a chap on Astrobin who considered this same project. In the end he decided that an MX+ would just not cut it, so he bought an MEII see
Hi Martin,
at the risk of opening an oft opened can of worms, the quote there
“Interestingly enough, although the C11 has only 60% of the light gathering area of the C14, it has a focal length of 2.79m compared to 3.91m for the C14. It is therefore faster and that varies with the square of the ratio of the focal lengths. Therefore I will end up with a 20% higher signal with the C11”
Is nonsense yes ? (you would get more signal from any target with the C14. it is then just distributed differently on the sensor)
Cheers
Robin