[Glenhuon (Bill)]

The central screw is quite a long one to allow for some adjustment of up/down position. Then you have to adjust the others by the same amount. Its surprising how little adjustment of the screws it needs to get things in line. Probably best to adjust in small increments as slackening it right off will allow the secondary to spin on its axis and upset the perpendicular secondary/focus tube alignment. If you look down the focus tube or cheshire and the secondary is pretty round and in the middle of the field of view its probably OK for position in the tube.
My 6" was due for a check so here's a couple of pics. I checked the position of the 3 clips on the primary using the cheshire as its probably more accurate. Cheshire was removed for pic. Put in the laser, centred the spot and adjusted the primary till the dot disappeared down the hole. Re-check the spot center, as mine is incline to shift a tiny bit when I adjust the primary and tweak the primary again. You'll notice the focus tube is out a bit so the end of it doesn't show in the mirrors.
Took 30 mins all up, but I've had a bit of practice now.

Hope this helps

Bill