Hi everyone,
Not much of a historian but I am a huge fan of old Errol Flynn swashbucklers! I have seen all his movies and read several biographies of him, including his excellent autobiography My Wicked, Wicked Ways. I was just doing a Google search and discovered this forum, and wanted to help answer Weelittledrummer's original question.

I also watched They Died with Their Boots On again just lately on TCM and I know those revealing early scenes you're referring to – it's when the young General Custer joins West Point at the very start, right? You can clearly see this obscenely large outline of his willy through the tights he's wearing! Lol. Later on there's a night-time empty barroom confrontation between him and another character, and Errol is wearing black trousers – not skin-tight like the tights earlier – and again he shows a massive bulge. Well, it ain't padding. That nude photo that was posted earlier of Flynn with a rather average-looking endowment is actually a well-known industry fake, albeit an impressively convincing one that has fooled many people so far. Supposedly Flynn never posed for any full-frontal photos in his lifetime (there are a few bare-chested "beefcake" publicity shots and a few of him posing in swimming trunks), but he would happily whip it out at his legendary house parties. Truman Capote wrote a biography of his friend Marilyn Monroe where he talks about the time she went to one of Flynn's parties, where he entertained his guests by playing You Are My Sunshine and The Star-Spangled Banner on the piano using only his willy! True story, and Marilyn confirmed that it was indeed huge even in its flaccid state. The estimated figure I have most commonly read for Errol's willy is a whopping 11 inches long, though two or three sources cite it as being 10½ inches.

Oh, and YES, Errol's studio bosses at Warner Bros. DID insist that he strap down that huge willy against his thigh to avoid "embarrassing protuberances" (their words) and had it written into his contract, though allegedly he got tired of performing this uncomfortable routine towards the end of his career and would let his willy run wild and free inside his tights. One quote has him as saying something like "If Don Juan didn't have to strap it down, then neither does Errol Flynn!" So to answer your original question, he WAS actually "strapped-down" in 1941's They Died with Their Boots On! Haha, guess they didn't do a very effective job of hiding it, huh?! Must be hard to conceal an 11-inch willy. For whoever's interested, you can also see undeniable evidence of Errol's big bulge in The Charge of the Light Brigade (1936), The Adventures of Robin Hood (1938), The Sea Hawk (1940) and The Adventures of Don Juan (1948). However in most of his other costume pieces he either wears those long frilly pirate-style shirts untucked over his trousers, or else is "hidden" by careful camera angles during the fencing scenes. According to the biographies I've read, this was also a deliberate studio decision.

An interesting pic from The Sea Hawk which Weelittledrummer may appreciate, hehe:
http://www.errolflynn.net/Miscellany/sh13.jpg