We were just having this conversation over in this thread. Rotational weight is where it’s at but weight at the hub (Schlumpf versus aluminum hub on Impulse) on my two similar 36er setups is noticeable. The Impulse feels light as a feather climbing hills. Also, you can’t (not “recommended”) use a FOSS tube in a drilled rim. Finally, I’m on the list for the lightweight tire if/when it comes out. I’m a weight weenie.