Patriot kit questions
If you build it stock and follow the directions, it will be plenty strong enough for whatever speeds you are likely to reach. I honestly believe you will have a faster Patriot with the Jett .50 since it is a much higher revving engine than the Jett .90 light. The plane will be significantly lighter with the .50. If you go ahead and put the .90 in it, you better be prepared to put lots of lead weight in the tail to balance it. It will be much easier to build using the .50 size engine since it will fit the plane without modification.