JMB designed the 1911 with a 5" barrel and that is how it should stay. Most of the 1911 'experts' are of that thinking for reliability and function. I think the Prancing Pony is the only way to go. RMK #1 in 8" blade as Bo's first examples were (actually a bit longer) and in leather. Stainless blade, LH sheath with handle keeper. Historically this would be the most accurate combination - stainless not historical but sensible.
If historical 'accuracy' is not critical, then whatever. Just don't go a short barrel in a 1911, and a 5' blade while 'cute' is a couple inches short on performance. We all know that many here suffer from that affliction, present company excluded.