Looks to be very well made... and quite attractive, if you're into the "attractiveness" of Glock stuff.
2.9 oz. added to a Glock, all things considered, isn't too much to worry about for anything other than perhaps a CC gun.
Is most of the additional weight via the use of the "Seattle Slug"? If so, then you can,
if they make the option for the Gen 4, add even more weight with the heavy slug.
Cheers,
C