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This system worked for me on the RN 8F8 build.
To keep weight and size to a minimum the rings are all very close to the optical axis and perimeters so any primary misalignment shows easily. Also aligning the wire spider was a mission in itself.
I had one of those Led torches like a small cylinder. It just happens to be nearly 1'25" diameter and slides in and locks nicely in the 2" to 1'25" adapter.
A piece of paper over the front of the OTA showed me where the cage and rings were intruding and got the primary aligned down the middle and also showed a minor mislaignment in the OTA rings, easily resolved. A centred cross on the paper got the secondary into the right position.
Still had to adjust the secondary position a bit as it got closer to the axis, one of the issues with a wire spider being the three axis movement any retensioning has on it. Now it's in place though nothing moves.
With the longer FL of the scope (f8 = 1600 m ) any mirror misalignment is magnified more. I found I was making too coarse an adjustment when I first started and overshooting the spot. Final tweaks were almost infintessimally small. I'm using my neoprene rubber block 'springs' which don't move so not expecting it to shift any time soon.
But the system certainly works.
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