I just went through the Horizon website, they apparently do not carry the .50 anymore, a search for a Saito .50 brings up the 1.50 and 4.50. The .40A is not listed but comes up if you do a search for it. I had a Saito .56 on a relatively heavy H9 Cherokee 40 for several years and and it flew it just fine turning a 12x6 three blade at 9,400.