It is possible, under some circumstances, to squeeze in more than 99 messages (depending on the terp). See more in this thread from a couple of months ago.
The trick is (as explained by @pdxiv):
The reason for this, is that in the .dat file format, the 4 commands are encoded as 2 numbers, like this:
(150*command 1 + command 2),(150*command 3 + command 4). This effectively means that command #2 and command #4 are limited to 150, 100 of which are available for use for printing messages. Not a very good explanation, perhaps.
My opinion on the matter, is that ScottKit probably should allow more messages when using commands 1 or 3, and scream bloody murder if you try to use too many messages with commands 2 or 4.