Large is relative! I have worked with large industrial power supplies all my life and have a way oversized collection of parts so for me a 500 amp diode and the 1#+ heatsink it is attached to is normal.
Now my 2200 amp 1200 volt Hockey puck diodes and SCR's and their heatsinks, Well now you're talking fairly big but not as big as the ones that have three 600 amp 1200 volt half bridge IGBT bricks on that can dissipate 2 - 3 KW's passively . Those are huge!
For a DIY 50 amp independent four diode full bridge or a two diode half bridge running near-continuous duty I would recommend using a good sized CPU heatsink on each mounted in a way to get reasonable passive airflow around them.
By touch of hand they may feel hot but by diode heat ratings they would be well under their critical limits.