Ask them what alloy of "aircraft aluminum" the base is made out of. I am very cautious any time I hear that term as there are many different grades of aluminum used in aircraft construction. Some are stronger than many steels, others, not so much.
The answer they give you should be a 4 digit number followed by a dash followed by "T" and another 1-3 digits. It would be great if they said 7075-T6, but 2024-T351 would not be so bad. If they can't answer the question, return the rail when you receive it and move on. Don't give them any hints.
Softer alloys equals less machine time and material cost for the manufacturer. If a manufacturer is using quality raw material they typically want to advertise it. Look at the Seekins website. They clearly state that they are using 7075-T6 which is serious material.