Jack Shaft Diameter?

[JoshTehSquash]

Hey everyone I'm installing a jack shaft in my Yerf-Dog so I can run larger rear tires, but I don't know what diameter to use. I'm either going to use 5/8" or 3/4". Is 3/4" considerably more durable? However 5/8" seems to be the standard, and 30 series TAV2 drivens have a 5/8" ID. Is the 3/4 worth the extra strength or should I just get a 5/8 to keep the option of adding a TAV?

 

[OzFab]

5/8" will do fine as long as the shaft is properly supported...

 

[KartFab]

I run a 5/8" on my Manco with 13 hp/40 series torque converter. Only supported by 2 bearings. Holds up just fine.