Wow! Congratulations!
I would set the focal length to 800 - only effects SR and you will probably have that turned off on a tripod anyway (unlikely to be hand holding this one!). Suggest using 2s timer or remote if you are not already - which will automatically turn off SR.
I see the minimum focus length is 30m - presumably your test subject is further away than this? Have you tried focusing with LV magnified yet?
Hope to see a review posted here soon:
Tele-Takumar-Super-Multi-Coated-TAKUMAR-1000mm-F8 :-)
P.S. Just saw the weight - 5.5Kg!