Back in the 80's, when I first saw a Chesini with internal cable routing, I dreamed about owning a Chesini just like this. I finally purchased one about two years ago.
I was very stoked about it. It rode well and the workmanship was quite nice. What turned me off completely was how amateur the aspects of the frame that were not visible from outside were handled.
By this I mean that internal brake cable that does not have any internal cable guide. To install the brake cable you need to insert your finger into the top tube through the seat tube, then deftly direct the cable to the hole in the top tube.
This is quite a let-down when you see how nicely other Italian manufacturers handled the same thing. But the brake cable routing is nothing when compared to the internal gear cable routing. You almost need an engineering degree to be able to install the cables. After all the hassle in dealing with the build, I never felt right about riding the bike. I had no where near the same problems building up my Rauler, Marastoni and Grandis bikes with similar internal cables, all of which were fitted with internal cable guides. Likewise, from an engineering point of view, I believe the Chesini design will lead to more water entering into the top tube and could lead to more oxidation.
As regards the aero Campagnolo brake levers in 1984, there were indeed no official Campagnolo sold ones available, but they were indeed around. I have a set of pantographed Record levers that have been modified for internal cables. You would need to drill the handlebars below teh brake lever clamp on the handlebars to fit them. They work, but not as well as teh Modolo Kronos ones. I have three bikes fitted with the Modolo Kronos levers, so I guess you can say that I like them
You know the more I look at your bike, the more I begin to forget the disappointment of my own Chesini. They are soooo beautiful!!! If only they had spent a bit more time in making them completely right... It is a bit like having a beautiful super car that has Vauxhall switchgear inside.
PS: I feel that as regards the internal cables, in some ways, the SL/SP tubing may actually be preferable to the SLX version, as the helical reinforcements made installation of the gear cables even more difficult.