Hi, just thought I would post this advice I received on CN site from Hiten as it may help anyone using the Meade 3.3 FR with the infinity.
The 3.3 FR works best at F5,
Focal length of Meade 3.3 is 85mm
So you need around 45mm of spacing to get F5.
take into account the infinity back focus of (12.5) /13mm
So you only need an extra 32.5mm of Focal Train to get F5.