I'm currently renovating a 1970's French Tandem (See http://gitaingaves.blogspot.co.uk/ and THIS forum thread, if you're interested), and am having a little bit of trouble picking derailleurs...

The proposed setup for the gearing is:
Front: 52-42-28 (Existing cranks)
Rear: 11-13-15-17-20-23-26-34 (This cassette)

This presents an overall (rear DR) capacity of ((52-28)+(34-11))=47 As far as I'm aware, the highest capacity any rear can officially handle is 45? We are very unlikely to every use the small/small combo, so a bit of slack shouldn't matter too much, my really question is, due to budgetary constraints, do you think we can get away with a 43 capacity (excluding the smallest 2 at the rear, whilst on the smallest at the front) without any problem? This one seems very reasonably priced...
For the record, I will need a claw adapter (included in the linked one, but around £5 separately).

At the front, It's a similar situation; (52-28)=24 is a larger capacity than most are rated for, and 52 is quite a large outer chainring! Does anybody know of a system that would work? The Seat-tube diameter (for clamp_ is 28.6mm

Thanks in advance for your help, which will doubtless be fantastic : D

Will