It is possible to load custom samples to Gladiator for OSC5.
1) Go to VST-Plugins/Gladiator2_data
2) Delete 058Burp.1, 058Burp.2, 058Burp.3, 058Burp.4
3) Replace 058Burp.gls with a 16-Bit mono WAV file with standart header
4) Load Gladiator and select 'Burp' in OSC5 to access your sample
It is also possible to resynthesize custom WAV samples for usage in OSC1-4.
A tool and instactions can be found here:
http://www.tone2.org/forum/index.php?topic=197.0