Mxsmanic wrote:
I can't find any guidelines on the type of fixes or waypoints to be
included in the routing description of an IFR flight plan. I presume
you can use things like VORs and (?) airports, as well as airways and
anything indicated on IFR charts or procedures. But can you also use
VPxxx waypoints or other VFR fixes?


The VPxxx fixes generally are rejected by the flight plan handling
computer for IFR plans. You can insert lat/lons in (easier by
DUAT, convincing a FSS guy to do it is a bit tedious).

The reason for asking is that I'm wondering if a VFR flight plan with
detailed routing that lists specific waypoints and fixes can be easily
converted to IFR without changing the routing, should weather or other
factors mandate a switch to IFR for the flight.


You can put anything you want on a VFR route. It's not used for
anything. it just goes into the computer and stays there until
you don't show up at your destination and close the plan. They
start calling around looking for you and if that doesn't yield
anything, they might start looking at your route of flight filed.
But really, they look more at how much fuel you claimed you had
and where you could have possibly gone based on where you started
from.