Somehow I pictured a six-sided tube: any thoughts on what the flutes "do"?
Spot-on colour choice for those decals!
BUT... I thought you were a Shimano-free zone?
The flutes are intended to stiffen the tubes, this is a technique used in industry but the benefits interns of increased stiffness versus weight are marginal in this instance. Columbus still do a fluted tube set, Gilco, which is used on steel Colnagos.
I've now changed the group set to Campag Chorus with the exception of the wheels and cassette, which are Shimano Sante. This gives me a 7 speed cassette with 5mm spacing shifted by a Campag 8 speed Ergos, which also use a 5mm spacing. Works perfectly and looks much nicer.
Chas Roberts in Columbus SL, Vitus 979 (Full Campag Veloce), Vitus 797, Olmo (Fluted tubing), Fondriest MegaCarb, Ridley Aeron (modern winter bike), Olmo Competition