As a Highland reenactor, I have a set of truibhis - they are correctly tight on the legs and "low-hinged on the ****," as Martin Martin of Skye described them in 1707. Whereas 17th/18th c. knee-breeches have tight-fitting legs and a baggy seat (to allow one to sit without putting undue strain on the crotch seams), these truibhis have no such baggy seat, which makes sitting an adventure. I can also attest that truibhis also MUST be gartered at the knees (the MacIan prints notwithstanding) to keep the weight of the lower leg fabric from dragging down the upper part. Usually, after donning my truibhis, I pull up the fabric of the lower leg as much as possible and garter it immediately - his not only relieves the weight dragging down the upper part (knees and up), but also provides a little looseness around the knees that make walking comfortable. I hold my tuibhis up with a waistbelt, on which I also hang my sporran and dirk. My tuibhis don't have the little cloth flap (purpose??) in front. Very warm in cold/wet weather. After researching the wear of truibhis, I have come to the conclusion that they were an expensive item of dress (being tailored) which the lower socio-economic levels of clansmen probably could not afford. However, that did not preclude truibhis from being worn by any man who could somehow acquire a set through raid, trade or whatever. Period drawings show clansmen wearing truibhis with belted plaids. Good sources for information are Telfer Dunbar's two books, "A History of Highland Dress" and "The Costume of Scotland"