Mm. Thanks, Ben. I'm a bit confused, as I'd imagined, from the tailor's drawings, that the seamless type was made in two pieces, one for each leg ...
Google books came up with "The Tailor's Preceptor" (good title) of 1826, which is rather post-period, but shows the relationship between pantaloons (formed to the leg below the knee) and what it calls "pantaloon-trowsers", which I think the rest of us would call trousers [??] and are cut parallel from the calf down:
"Pantaloons are formed from the knee upwards by the same rule just laid down for breeches ... form the remainder of the leg-seam according to the measure; mark the bottom by a straight line; and hollow the underside as in breeches.
Fig 2 also represents pantaloon-trowsers. These are usually cut the same width at the bottom as at the calf, and may be formed by the same measure, from the straight line at the side. The bottom of the fore-part may be cut a little hollow, and the hind-part round."
Does this help? Maybe not.