Quoted from RWH:I'm not sure those two FH and Taxi can even be changed
Yes they can be changed to 4 or 5 ball I believe.
For me, all my pre-1986 games are usually set to 5 balls, just because most of those games will drain faster, and that's how they were set in my local arcade back in the day. All my post 1986 games are set to 3 balls, due to slightly longer ball times.