JMS/MQ sender channel: max length for MQ msg for fixed length conversion

We need to know the maximum line length for JMS/MQ adapter configuration.

We will get fixed length data like

field1field2field3field4 where we interprete field1(0-5), field2(6-10), field3(11-15), field4(16-20) and so forth.

What is the maximum amount of position for fixed length parsing? e.g. field5(21- maximum)