Congratulations of getting this elusive item! I'm not surprised as to its quality as the similar vintage 800/8 ED non-If is razor sharp. The 800 is even more elusive than the 600, by the way, with less than 100 units made. The non-ED 600/5.6 heads are more common and deliver sharp images as well, but the chromatic aberration is pretty obvious and can be bothersome to get rid of.
Two aspects worth keeping in mind: firstly, these lenses are *long focal*, not telephoto, designs. Thus their overall build length is very long. Secondly, due to the weight and weight distribution, they put a significant stress on the focusing helicoid of the CU unit. In fact, the CU is not really suited for the 800 (and 1200) lens heads as the focusing tends to bind. Thus the AU-1 is the preferred unit. With the 400/4.5 head, there is no problem and either focusing unit can be used. For the 600, the CU does the job, but the AU-1 is perhaps more suitable.
Here is the 800/8 ED + AU-1. A very sturdy tripod is mandatory and a large fluid head is excellent for support.