No you can for sure cut the complete silence, you just got to leave everything even if it's -120 dB in, your signal gets folded with the impulse response. If the IR is = 0 there is nothing to fold. You can also test this if you want but i am pretty sure you can cut every sample that says 0 on...
you can find one here: https://sourceforge.net/projects/hesuvi/files/optional/HeSuVi_rec_IR_pack.7z/download
use dirac_delta_mono.wav
edit: i once made a tutorial how to use this technique to get Dirac Live room correction for free, the concept remains the same, beginning at step 5:
Ok, i just registered to give you a very simple and 100% accurate solution to your problem.
On a windows machine, just run a dirac delta impulse through sonarworks and record the output. It will be a very short click. (Essentially it's just one sample at 0dB). Save the output to a 32 bit wav...