geof is absolutely correct. Going thru the whole process of smaller to mid power stuff up to G is essential and fun. Its the building blocks and the traveling the journey of the Motor power alphabet that will also provide for larger stuff as well. in your case though it sounds like you have at least one if maybe not more youths that are in the age range(14 to 18) and already they sound as they have low and mid power experience up to the G motor level of stuff. Id say again as I said before in a previous post go for it have fun and learn. Be sure to have them ask all the right questions and learn the correct skills needed to build high power projects as that again will pave the way. I would even recommend a mentor program or even just coming to launches and looking at what others do and asking questions before actually building and flying. Sounds like with the right direction of work and learning they will be on their way.