Acp pinpoint advice for 2800fl required.

Hi,
I've spent the last couple of years using an ES80 fl600 and have just changed over to the C11 with fl2800 (possibly adding a 0.63x focal reducer).
I got errors in pointing of between 1 and 4 minutes.
I've got both the gsc and USNO A2.0 Catalogues and have the USNO A2 selected.
What are the main points to take into account when switching to a higher focal length?
Obviously the ed80 was easy as it was at worst a 4 arcmin error in a 30arc min field of view.
I do seem to have an error in the C11 optical path as one of the few successfull results i've had displayed an fl of 3174 but the ra and dec spot on, i suspect i rotated the corrector plate when assembling the c11 so that it's now not matching the mirror.

As ever any comments welcome otherwise i'll just keep plodding along and playing.
set up the focusing last night and it's working well.
Finally managed a guider calibration after hundreds of guide star not found messages from maxim dl, which is very frustrating when you can see 6 really perfect ones on the sensor and it ignores them.
The C11 looks great on the mesu I'm looking forward to doing a horses head this winter if i get a clear night.

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ACP was tested extensively on an 0.6m f/10 (6000mm focal length) RC Optical. Guiding was the biggest challenge. The huge, heavy RC fork mount is a beast. Eventually the Bisque control system was replaced by a Sidereal Technology system with Reneshaw encoders. What a difference!

I had rotated the plate resulting in an error in the optical system and incorrect focal length.
I've fixed that but now have to colimate it again, the stars are like seagulls at the moment.
I've got an extension tube at the post office which will give me the 105mm spacing i need for the focal reducer. I'll do that when i get bored of fighting with the c11 at f10.
i've got pin point working within a certain pointing error range but will need to check for any mirror flop or movement.
It's a lot more fidley than 600mm!

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Just use the A2.0 and also expose deep enough to get to the mag 17+ stars that the A2.0 has to offer.