sane max value for message size in 2023?

[AJ Weber]

I realize this is very much an "it depends", but recently I'm getting a 
lot of messages bypassing spamc because they're a few KB over the 
default, 500KB limit (spamassassin 3.4.x).

Can I bump this to maybe 750KB, and if so, will spamc read that from one 
of my .pre files, or do I have to somehow add that to a scan command-line?

Thanks in advance,

AJ