Finding a 2x4 in a taller size is a challenge - most stop at 60" tall. Upon pondering this, I realized that a height of five feet means it can slide neatly into most closets because the coat hangar rails are set a little higher than that.
And five feet is not a lot, if you plan on having your fan and filter inside the tent. Your canopy is going to be pressing against the light before you know it.
Taller models I found were a Mars Hydro at 71" (just under six feet). Spider Farmer has a "2x4" advertised that's actually a little larger - like 55" x 27", but it goes to 80" tall. It's advertised as being made of the same 1680D cloth as Gorilla tents and also has a $20 coupon on it at Amazon, making it $159.
The only 2x4s I found that go higher are Gorilla, Goliath (a Gorilla clone that offers the same pricing with less warranty), Octane, and a brand called Ultra Yield. The Gorilla, Goliath, and Octane are all in the $230-250 range, the Ultra Yield is cheaper but there were so many stories about busted zippers in the Amazon comments I figured I'd spend a little more to avoid a potential headache. All of these options use the stronger fabric Gorilla uses.
If I had stuck with The Plan I'd have opted for the Octane, but, alas, the space I thought I had for a 2x4 turned out to only be 47" wide and none of them would fit. Wound up getting a Gorilla 3x3 since Octane doesn't make that size.