This is the first one cut so we tried a few different finishing patterns. the far end was cut all the way down with a 1" end mill, and then fileted with a 1/4" 4 flute end mill; We had to run really low ipm's though because it kept deflecting we kept loading the cutter with chips.
The near end turned out much nicer when we got a short and stubby 2-flute that we ran at 80 ipm (We can still run faster, we just wanted to test everything) and made a much nicer finish. We still used the 1" to rough it, but we didn't go all the way down, so the 1/4" still made the final pass.
Now, 1/4" seemed small to me.... but the instructor at the shop really, really knows his stuff; so I'll trust him
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As for the size, the finished product will be .375" x 5" x 37.5" for all the rails. Also, 233 was definitely an influence.
Thanks for the comments.