The spin-on Filter is the secondary Filter. If the fuel is so cold that it is having trouble passing through your 10 micron stock spin-on Filter putting a larger 2 micron Filter may not work because the 2 micron one is just going to pug up easier.
In this thread there is to filter mods:
http://www.peachparts.com/shopforum/diesel-discussion/225004-lower-micron-fuel-filter-mod.html
In the Deliveryvalve mod will also work with a VW Rabbit (from the 1980s) filter and that would give you a about a 2x as larger 10 micron filter.
Also with the CAT filter mod I think there is also a 10 micrion filter that fits it but I don't have any filiter numgers to pass on.