Looks like my FR IV reduces, I haven't bothered making any exact measurements.
Pix below were taken at twilight in order to post them asap, bit of smoke haze around. Both are 5x stacks with 5s exposure in Neb, and levels adjusted in neb and then saved as jpg's. Used Paintshop to reduce the jpg's by 75%. Pixel measurements are the same, 760 x 503.
I forgot to note the centre star, I think it's Eta Lup. Both pics taken within 2 mins with no scope recentering needed.
Note: No FR needs approx 8" of back focus with QHY8, with FR IV, direct connection plus 50mm T extender from FR to QHY8, so this would be a bonus in not needing the longer back appendages to gain focus with it. The FR pic also looks better
Hope this helps. Let me know if you want the RAW pics for better measurement.
Cheers,