Opening the bottom of the helix will not void your warranty and Line6 has published a guide on how to fix the squeak yourself. http://line6.com/support/page/kb/_/effects-controllers/helix/helix-pedal-maintenance-procedure-r861
Opening the bottom will NOT void your warranty and Line6 has published how to fix the squeaky problem yourself. http://line6.com/support/page/kb/_/effects-controllers/helix/helix-pedal-maintenance-procedure-r861