Honestly, if you get the correct files (double check once everything is on your system) then there's no reason you should brick unless something crazy happens like your SD exploding. The method is definitely sketchy, and will more than likely take a few tries (my N3DS XL took like 8 tries, but once launched the sysUpdater, it went through smooth as butter. The real pain is getting all the CFW sorted out since there's so many options.
I say go for it. You don't know when another opportunity like this will present itself; and that expected 10.4 update will make this tougher, since you wont be able to recover your system from a soft brick back to 10.3 and try again (it'll go to 10.4).