sv550 1x field flattener woes

From here, we can see that using the ff meant for the 102mm f7, we need less backspace,
Here we are at around 50mm from the m48 thread. Better than at 55mm. Still thinking...

globular cluster m13 in hercules
veTEC571 on sv122    26x4min @ hcg100
process StarTools

process SetiAstroSuite

vega
6x10s

focus settings