I own two other M series Lum-Tecs, a M49 and a M24 (app. the same dial size as the M53/M54s). I also own a Panerai 176.
I just measured, the dials on both are almost exactly the same size, the 176 maybe .25mm bigger. The hour hand on my 176 is app 9.75mm long, the hour hand on my M24 is app. 9mm long (.5mm difference, taking into account for the .25mm bigger dial on my 176). The minute hand on my M24 reaches to about 4mm from the edge of the dial. The minute hand on my 176 reaches to about 4mm from the edge of the dial.
As far as I'm concerned, the length of the hands on my 176 are as close to perfect as you can get. The length of the hands on my M24 are almost exactly the same length. FWIW, when the hour hand on my M24 is at the 6:00 position, the tip of it is only 1mm from the 6 on the dial, plenty close. The tip of the minute hand is maybe 1.25mm from the minute markers, plenty close.
IMO, the hands on the M53s and M54s will do just fine. No disappointment here.