My old flying partner Bill Rich had made up a set out of PVC, with a "H" type stand, so they were portable, and he had them painted bright safety orange between 4-6ft. He stored them at the field... they are probably still there, and no one (at least not the RC guys) probably even know what they are.
I used them a few times... yeah, humbling. My Nobler size planes, and my PA40 pipe plane would do it easier, but a 75 size plane with an 18" tail moment with a 13.5" 3B prop, well, it's going to take a lot of muscle, look cramped and feel rushed. Your flats in the squares will "feel like" they are 3 plane lengths long, heh.
I had got to where I could keep the width in there like with the SQ8, but I unconsciously ended up cheating the height to buy more time, and that totally distorted the shape into what Owen Richards used to call "butt cheeks"... I finally fixed it at the NAT's one year with the help of Fitton, over my Cell on a Bluetooth headset, with him watching and telling me "wider!" "Wider!" "WIDER!!!" as I did the SQ8 over and over and over until I got them proportionally square again.
My minds eye had gotten so used to looking at them wrong, that it took a lot of convincing to get me to believe that these MUCH EASIER to fly SQ8's were correct... but my scores that day instantly reflected the improvement, so there was no arguing it. The judges much prefer a very slightly larger but properly shaped SQ8 with good intersections and bottoms over a messed up smaller one, go figure, heh heh.
A few people I know could do it and make a rulebook SQ8 look "normal" or contest worthy because that's pretty much how they fly anyway, the rest of us mere mortals, well, yeah, tough stuff. I'll say one thing, to my eye, it's not "pretty". A rulebook pattern looks abrupt, and very workman like, but not graceful or pretty. A few guys I know fly pretty patterns, and they have a rhythm to them which I really enjoy watching, but are they 100% ruelbook? Nah... but I enjoy watching them better.
I think every serious competitor should try the markers at least once... maybe with a disposable ARF Flight Streak or something, and your ego in check, heh.
EricV