pictures with barbs installed and next to it is dremel with sanding band, what I did was drill larger the hole and sand it to the size of G1/4. DO NOT use the size of G1/4 drill bit to drill or else you will damage the threaded part very easy so use the smaller size of drill bit so the drill bit does not touch the threaded part and drill out larger hole then using sanding band to sand it to the same size of G1/4 or larger if you want, this is my way of doing it without worried about damage the threaded part so maybe you guys can come up with better way so please share with us

NOTE: Always drill slowly when working with acrylic, as for sanding part you can sand it @ 1000 ~ 2500 RPM (cordless dremel)