Mixing integrated levers (brakes/shifters) and bar-ends is very common in the tandem world. There are just too many things to control (front derailleur, rear derailleur, front brake, rear brake, drag brake).
I've tried all kinds of setups with the tandem. I started with two integrated Shimano shifter/levers to control the front and rear derailleurs, and the front and rear brakes. I set up the drag brake on a bar-end. While using Shimano STI or Campy ERGO integrated levers isn't completely annoying for adjusting the front derailleur trim on a single, its VERY annoying on a tandem. There are just too many things to control, too much to be resonsible for to have to worry about finicky shifting that is only compounded by the fact that you can not, on a tandem, look down at the front derailleur, to gauge the trim corrections.
When I switched over to a friction bar-end to control the front derailleur trim on the tandem, which admittedly has a much much wider range of gears than just about any other bike will (easy to spin even a 54/11 out, and a 22/32 never feels low enough on the really big climbs), I realized how much I love friction front trim, and how much I truly hate indexed front derailleur adjustment. I've never liked the expression "a solution in search of a problem" but front indexing certainly fits that mold. While I could have used the integrated right lever to control the drag brake, with a lot of bikes I was worried I'd get confused and forget and set the drag brake while trying to drop to a smaller ring. So I took of the integrated right lever and replaced it with a purpose designed brake lever. What I discovered is that "real" brake levers do a MUCH MUCH better job of braking, and modulating the brake than do integrated levers. I was absolutely astounded at how poorly integrated levers are at actual braking. Now admittedly a tandem is an absolute acid test in terms of braking. The brakes are being asked to do "double duty" so to speak, but I realized that when I removed the Ultegra 9 speed STI levers from one of my singles and replaced them with "real" brake levers that the difference was still night and day.
The really funny thing? Even top end kit like Campy Chorus/Record or Ultegra/Dura-Ace actually weighs less as levers and bar-ends, or bar-end shifters on Paul Thumbies, or downtube shifters on Kelly Take-Offs than they do as an STI or ERGO integrated assembly. I've never had SRAM Red so I don't know if this holds true for those as well. However finding weight savings on any bike is always welcome in my world. Yeah, yeah, I know how funny it is for a fattie to be worried about grams on the bike when he should be worried about pounds on the cyclist. At any rate dedicated levers and bar-ends (or downtube shifters on Kelly-Take offs) were ALWAYS lighter than my original STI (or Ergo) set up, and ALWAYS gave more control in braking, and allowed every bike to stop faster. What came as an absolute shock was the fact that the shifting improved to boot. Obviously, the front shifting became quicker because you could quickly shift by 'ear' and feel after riding a tandem for any length of time, but the rear shifting improved markedly.
It turns out that shifting isn't nearly as exact or precise as we think it is. Even on the Ultegra or DA stuff I was taking off, the integrated indexing was largely dependent on the Shimano patented "floating pulley" to compensate for how 'finicky' 9 and 10 speed stuff is. It turns out that in going to Bar-ends or downtube levers the shifts just became more precise, less 'finicky' (though still not like 7/8 speed), and just crisper.
So the moral of the story is that I'm now a HUGE fan of Kelly Take-Offs, which I use to mount downtube shifters near the levers for a lighter, and better approach to "integrated" controls. I can not tell you how much I love having crisp, finicky-free shifting within fingers reach of the hoods, although I do use bar-ends on some bikes instead. I'll never have another bike with 'indexed' front shifting if I can help it, to the point that I went with old XT thumbshifters on the mountain bike to boot...
This also started my expensive hobby of collecting epic brake levers like my Mavic 430 SSC levers, and my pursuit of the non-integrated Campagnolo Record carbon levers.
Anyone who wants a screamin' deal on some integrated levers PM me.
For those that haven't seen the Kelly Take-Offs here is a link and an image along with a link to Paul thumbies. You know what STI, Ergo, and bar-ends look like (though Riv has some bar-end pods that take downtube shifters, so I've included an image of that here - and a link), lastly I've included a pic of my Mavic SSC dedicated levers, which I found for sale on the Belgian eBay, they are NOS, I haven't had the courage to mount 'em yet:
Rivendell Bar-end (con) pods