Yeah thats what I and many other lucky Captains did XXL - under the seat. Why are we lucky? Because MiamiDave, in his fine humanitarian style, already wrote a how-to for the Triple K&N conversion AND secondary plate removal, complete with photos, that even a mechanically brain-dead office type like myself can follow, and laid it right in our laps. It is here:
And you're right on with Travelguy's pipes. They're way cool.
Triumph US may have a problem with putting the bottle under the seat as they say may not work correctly under some circumstances... We used a 955i bottle ($60 USD) and put it under the tank... So I still have my storage space under the seat and a config. supported by Triumph... Check out this thread:
wimmer or somebody else makes a long cylindrical "good -lookin " oil cooler that mounts to downtube on frame. could be used for overflow i suppose, if looks are an issue. ole wadejusa just eliminated the **** thing if i'm not mistakin by just running hose to bottom of bike.(??) he was also using some type of racin coolant also. ( didn't need overflow!)