I use the bridle butt for the front, back, all strapping and chapes, and the shoulder strap, the gusset, and any pockets are made with the thinner bridle 'lacing hide', also from Sedgwick. Shoulder is available at about a third of the cost of the butt, but is a much looser fibre, and weaker, and will tend to show stretch marks. Because these cases are 30 - 40 hours work, the extra cost of the bridle butt is worth it, in my opinion. This leather is the best quality that I have had the pleasure of working with in 30 years, and i have worked with leather from most of the tannery's in the UK, past and present.
This was to show a client the difference in colour between the London colour butt, top, and the Light Havana butt, a light havana lacing hide bottom. The Butt is 4mm, the lacing hide is 1.6 - 1.8mm.
The client chose the light havana, with a cream thread and chrome plated brass lock and fittings.
the partitions were the bridle butt, with a pocket grouping taken from my underarm folio's.
best regards, simon