Some reading on this thread. Post 9 has some details on my filter setup.
https://sprinter-source.com/forum/showthread.php?t=45146
Here is how I mounted it. I don't think you need 2 filters. A single would do well.
https://sprinter-source.com/forum/showpost.php?p=442616&postcount=157
I would suggest a filter than can be easily changed, like the spin-on unit I used in the above thread. Your sprinter can handle an extra 4 micron filter in that large size without issue.
This filter is a good choice. 10 micron, water seperation media, and drain to allow checking for water or cloudy fuel. Carry a spare. This type of spin on filter is used on many types of heavy equipment. So equivalents should be available the world over with some looking about.
https://shop.donaldson.com/store/en-us/product/P551001/20570
You could also go with a 3 micron with water seperation and drain such as P553207. This would likely mean you would not need to change your engine mounted filter for a VERY long time. I have 3 micron pre-filtration, and I have over 65k miles on my engine mounted filter. This filter is annoying to change compared to the easy spin-on filters.