That spaces the elements less than 1/10 wl apart at 14.2 MHz
(actually only about 0.07 wl) which seems way too close to me.

Don't say "It seems." Run it on a modeling program, but remember it is only
tuned for one frequency, you can tweak it for gain or f/b. I think if you
don't need any bandwidth (well at least no more than 3 KHz) you can do quite
well with a short boom.

When you consider a SteppIR you need to throw out the old conventional
thinking, ecause you have the flexibility to reconfigure the elements the way
you want them.

I have a 3 element SteppIR. It is on a 16 ft boom. My HyGain 4 ele on 20 and
5 element monobanders on 10 and 15 had cleaner patterns than the SteppIR, but
they were 1.5 times as big. And they didn't work 12 and 17 meters.

Rick K2XT