My answer is still the same....Warne and Millet....followed by Luppy's. Have Luppy's on my 7mm Rem Mag, Warne's on several rifles and a 270 WSM...and Millet's on my 300WM and 270 WIN. All have performed very well, but Warne's and Millet's take the slight lead IMO.

For a 50mm objective would I need high or extra high Warne rings?

High should be fine. Double check the Warne ring chart:
http://opticscamp.com/pdfs/warne-scope-ring-chart.pdf

Not sure if it helps in this case, but here's a quick and dirty guide on how to determine ring height:
http://opticscamp.com/content/9-meas...pe-ring-height

It might also depend on the bases you use...my Savage Model 10 FLCP-K has a Swift 6-24x50AO on it with an EGW one-piece "rail" base and I needed to use Medium Warner rings...where as with a Nikon 3-9x50 on my Remington 700 BDL using Warne 2 piece bases I needed Warner High Rings...