As mentioned; 127 is max but there are other tricks .. like actually Create a Click Track with a drum kit.
I have a file called Click.Mid that's 100 measures of sidestick on the quarter notes. Works great! You can also just create a track of quarter notes on the sidestick and copy it the length of the song. This allows you to use the methods below.

Trick One -
Insert PGPeakLimit on the track (yes even though it is MIDI; if it is a softsynth, PGPeakLimit can go in one of the lower FX slots) and boost the output slider.

Trick 2
This is most often used here; convert the click to an audio track using the sidestick as the instrument (Db2 is the note usually)
Then you can easily use any audio FX to boost, route it to it's own subgroup or output or employ any number of other tricks to make it louder.

/I love hearing a drummer say "I need the click louder" .. then making him cringe when I do

Using a click in a live setting taught me lots of ways to accomplish how to get it like you need it. PGPeakLimit is the easiest and quickest go-to method I've found in RB.

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PGPeakMidi.jpg (60.53 KB, 41 downloads)
I do not work here, but the benefits are still awesome
Make your sound your own!