For only 50 or so taps I think I would go with 1/2" mainline. Just because I think the 3/4" might cause the sap to heat up more on a sunny day. The 1/2" should run fuller and help stay cooler as it goes through the line. If you were using Vacuum then use 3/4". Either way make sure you hang it in wire and keep the line as tight as possible.
Jeff
470 taps
Torr Vac TV40D High Vac with Lapierre Horizontal releaser
Leader 2x6 Patriot raised flue
Leader 2x4 Steamaway
Wildfire arch
MES Dolly 300 3 post RO
DG 7" 5 bank filter press
and still lookin to get bigger