I routinely fill and weigh the basket out of the pf., level, drop in pf and tamp.
I just received a Strega using 58mm baskets. My tampers are 49mm.
I happened to try tamping with the included with machine classic thin light plastic (slight curve) tamper and the basket cupped in my other hand and then dropping in pf and think I really liked this method.

Actually seemed more natural feel for even packing of the basket. Could see better what i was doing and adjust pressure from both hands instead of just hard on the tamper. I'm finding it fast with less fuss and good results. The 58mm SS tamper base arrived today and I tried using it with basket in hand and it was very awkward. Works best the normal way.