You're right there. The Peli 1510 is a wonderful size as a kit transporter for aircraft hand-lugguage - I use the Foam-Inserts and not the padded-dividers
However, the limited dimensions restrict the amount of gear you can actually carry.
I bought mine in Birmingham - UK at the In-Focus exhibition at a reduced price, knowing that I would be using an additional kit bag - specificallly the KATA DR467 backpack.
As I now travel alot I have since decided to break up my kit into 2 types for convenience:
a.) STUDIO-only: Full-Frame - 5D, 1 x 580ex II, 17-40mm L, 50mm 1.2L & 85mm 1.2L II
b.) TRAVEL-only: Half-Frame - 40D, 1 x 580ex II, EF-s 10-22mm 100mm 2.8 Macro & the 28-135mm IS USM lenses. An MT24 macro-flash, 2 x cable-releases, 1 x AA battery charger with Car Charger adapter, SAN disk card reader, Canon USB & Video cables & CF cards x 12 all fit into the Peli 1510.
A Joby & Velbon tripods, 2 x Pkt Wzrd TT5's, Cokin filter holder with x3 filters, Canon Battery charger, a host of cables, adapters and 'what-nots' are packed securely away with my Laptop into the KATA bag. This KATA bag is then packed into my main suitcase (which is quite large) and is transported as 'checked-in' lugguage.
I have taken the decision beforehand to leave my STUDIO gear precisely there at home. This kit is far too heavy to lug around and far too expensive to replace. As for the 'TRAVEL' kit, the KATA bag was bought back in 2007 and is unable to carry my newly acquired capacity. The recently purchased Peli is a similar size to this KATA bag, as the Peli is tough and durable and 'flight-ready' I am happy to lug both bags. For the actual shoots, I take a no-nonsense (and regrettable) approach - '... take what I will defo' use ...' leave the rest and make-do without! - Always so difficult and in Suzy's words "... A real dilemma ...!"