I cant see the logic in placing a finer filter upstream.
If this new filter is filtering down to say 2 micron, nothing is likely to catch on the 10 micron. It is normal to have filters finer as you go.
Using that principle, one would place the 2 micron after the secondary filter, before the IP. This would maximize the life of both filters & minimize plugging of the 2 micron. That is what is done with large diesels in earth moving applications.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving