its not a problem, the challenge is good. If we cant do it we can't but we are going to thoroughly research and try out the idea before we say it cant be done.
For the spark plug tube, would aluminum be acceptable or do you want steel specifically. The reason I ask is that steel is alot harder to machine.
I think Aluminum 6061 will also do the job right. Aluminum 6061 is very strong and very light weight its the grade commonly used on aircrafts.