Custom, you could use a 1 oz weight in the spinner, or a heavy nut, and that would go close to puttin the CofG in the right place for alot less added weight.

I picked up a Skybolt kit from an estate a couple of months back; finished the build up with just covering to go. I've weighed everything that will go into it including covering, and figure it will be 7.5 lbs ready to fly, before fuelling it up.

I have an OS .91 Surpass II for it. Hopefully be flying in a couple of months.