Apologies for opening this 2-month old thread, but I'm almost in the same boat (ie MSI Tomahawk B450 and Arctic 34 esports duo), albeit with a twist. Installed the AM4 specified standoffs of the Arctic kit on the MSI backplate, BUT it was not possible to install the Arctic at all. The reason was that the standoffs were not tall enough to be extruding sufficiently from the holes on the Arctic kit. In essence it was not possible to put the thumbscrews, without applying
excessive pressure on the four corners of the cooler! If I understand correctly, you are having the exact opposite experience here??? Do you have the "plain" Tomahawk or the
Max variant (which is newer)?
In any case, I have the plain model and contacted Arctic who informed me that MSI Tomahawk B450 owners have reported the same issue to them! To handle that, Arctic is providing modified backplates and standoffs. From the Arctic support mail:
... (I) send you two brackets (different protruding threads) for AM4 with some different standoffs that would be also for AM4, but they are a little bit longer in size. Maybe that solves the original issue with the short screws.