CG's?

I have a Sterling Yak 9 with a Fox 35 and a Sterling Ringmaster Jr. with a Fox 19. They are so nose heavy that they point straight down! Where is the CG on these models? Is it normal to put lots of weight on the tails to get them to balance?

No, it's not "normal" for Sterling kits to balance that noseheavy; you must have gotten a couple of the good ones! Somewhere about 20% back from the leading edge at wing root will be close.

Also, move the engines as far back as you can. This may require a different tank setup.

Yak-9: front leadout.

Ringmaster Jr: Too much engine there! Used to fly those with Cub .19s...although that was back in the Dark Ages. Start adding lead to the tail with yours. WAY too much engine.

In the past year I have built a: Ringmaster, Ringmaster Jr., Akromaster, Bi-Slob, Buster, Flying Clown, and a Lil' Duper Zilch ...

ALL were nose heavy.

I expect that my Twister (presently under construction) will also require some tail weight.

You and I need to get together and build tail structures for each other. Mine always come out tail heavy.