I set my 20mm finest fans at 44mm. I face lather exclusively. I would say 48-50 would be the max loft I would set for that knot.
Set the knot with a dab, ( just a pea sized amount) of RTV silicone and you can try different lofts. If you want to change the loft a firm pull and the knot will come out with no damage. I actually use RTV for my final set as well. I just use a little more of it, ( I cover the plug entirely for a final set).
Thanks Mike & Dan. Looks like 45mm is a good place to set it. At least that's where 2 pennies puts it. I was gonna use the clear RTV silicone. I really like the Permatex brand.