Ok. If you want to make one yourself I appreciate that a 'simple" design with wide panels does appeal, however you are not going to get a shelter capable of standing up against high winds that way particularly for a tall structure.
(note the beefy poles in that Marathon and that is how they could take some weather...)
Also do keep in mind that the more we play with a type of product , the fussier we become.
So no doubt when you tried that Marathon years ago it would have felt a better tent than it would feel now.
For example, at the time it was an "Ultralite "tent. Now a 1.8 kg tent and in particular the better (for bad weather) designed Mark III at 2.7kg are not even "lightweight"
I mentioned this before, several times, so bear with me..
If you make something more than a tarp and intend to do that to save money, don't.
However if you do that for fun (as a pass time/hobby/challenge) than do.
One somewhat similar shelter would be the S2S Duo or the SMD Trekker/Scout.
The side entry point allows for shorter panels , sill they are of a fairly simple cut.
with front entry and no extra poles you have a very long unsupported area so you need a lot of tension to make it work.


(I can't tell you exactly the wind speed but small branches were falling off the nearby trees)
Note the difference in the same wind with the Contrail set up as it comes and with an added center strut ( a pre-bent tent pole or a "triangle as with the Moment will do the same)
and a front guyline.(the point here is that a boxed end is not all that good to create enough tension in strong winds)
The top is made from three panels , the seams act a bit like a built in guyline when tension is applied to the corner struts.
Anyway, something for you to think about.
Franco