I found that the bkl 260d4 mount is one of the better ones available and made in the U.S.A. I tried the cheap rws mounts made in China and had nothing but problems with it! Replaced it with a bkl one piece and hasn't move. The d4 (.004) takes in account for the droop in the barrel. also available in d7. But the d4 work great!
BKL 260D7 (with a little more droop compensatin 0.007") on my 350 .22. I would go for the D7 in case the D4 does not provide enough compensation. Every gun's barrel has different droop even though it's the same model. I think you 'd be much safer with the higher droop compensation mount. This mount is very solid and the most widely used one with 350's.
Do a search. There has been much conversation on many different posts about mounts, and specifically the 350. I agree, stay away from the RWS adjustable mounts.
I'm trashing my cheap Leapers one piece 3 screw mount and getting a BKL 260D4, but I already bent my barrel back straight...get the 260D7 and you won't ever have to think about it again! Straightshooters.com has them in stock today.
Sportsmatch Dampa Mount: superb protection for all your scopes, once fitted and well adjusted later on hardly any adjustment in windage needed anymore ! Best regards from Johannis.