Gotcha. I have a friend that is 6’4″ and he uses a Duplex, but he may lay somewhat diagonal too, I’m really not sure. As far as I know though he has only used it for himself, so no second person to share it with.
I will say that I have a 2012 model Copper Spur UL2 and when laying in it with a long (78″) NeoAir and a 20F sleeping bag I am completely end to end. I have also shared this tent with my wife (5’2″) and there is more room at the ends in my Duplex (also worth noting, I utilize the wall pull outs on the Duplex to give me more height on the walls). Like I said though, the CSUL2 is a 2012 model, and I know there has been some changes to them since then, namely weight reductions, however, there is definitely more length in my Duplex than in my CSUL2. If you haven’t already, I would suggest finding one and lying in it first with your sleeping pad and bag. Of course, with some places (such as REI) you can order it, then set it up (in your living room) and if it doesn’t work out, simply return it.
I will also add that I once bought a MLD Duomid. It was a beautiful traditional shaped mid, and bombproof. However, for 2 people I found it was a fail, and I now realize this would be true (for me) in any mid, at least one that opens on the side rather than the ends. My problem was the person in the back has to crawl over the person in the front to get in and out of the tent, which is a pain for both people. Also, when opening the mid in rain, the persons gear in the front gets wet because the mid opens over the front persons space. Having a door on each side would eliminate the problem of one person crawling over the other, however, it would still not solve the persons gear getting wet if opened in rain. Let me be clear though, I am not knocking mids, or the Duomid, at all! But for 2 people, they don’t seem practical, at least not for me.
I do wonder how something like the Trailstar would work though. It appears that it would be a better solution for 2 people than a traditional mid since it somewhat comes with a specified door space that isn’t located over anyones sleeping space. However, a Trailstar may require a bit more room than a traditional shaped mid to set up… Honestly, it’s been a few years since I have really looked at any of these so I am going off of memory…
Something else worth mentioning. If you do find a tent that works for you but the poles are too long, you can always order shorter poles from places like Quest Outfitter and build them on your own. They sell carbon and lightweight aluminum poles, as well as the other components to finish them out. It should be fairly simply to use the existing poles as a model to build the new poles. As a bonus, you would also end up with 2 set’s of poles!
I also see you are giving hammocks a try, and to be honest, if you can sleep in a hammock, that would be a great way to go. I just can’t do it… but it would allow you to forgo any poles, and would be easy to pack away, although in cooler weather you may have more fluff to pack since you will have both under quilts and top quilts. Then of course with hammocks, it will be even harder to find a set up that will work for 2 people aside from each person simply having their own set-up.
Also, like you, I don’t plan to use panniers. The setup in the photo above is how I plan to roll, however, I have added a jerry can to the tup tube under the seat and a Nalgene bag under the down tube to carry an extra liter of water. I really don’t want to carry a backpack on the bike, so I’m trying to find ways to carry more water on the bike, although I don’t want to add cages to my fork either. I also added a stash pack near the top of my down tube that has bike specific tools and repair kits in. And last but not least, I added 2 feedbags to my handlebars to carry an extra Nalgene and another for daily snack… I’m not sold on these though as it makes turning the handlebars a bit limited and just feels weird… But, like I said, I’m just getting into the bike packing thing. I have been backpacking for 10 years now and have honed and lightened my kit, now I just have to transfer that over to the bike!
Anywho, good luck with your search for a tent! I think this is something that many of us continue to do… we may find one that we get hung up on for a while, but eventually that may change too… good thing there are lots of options now days! :)
(And edited to add, I am not trying to push any particular brand of product, just sharing what I have found over the years, and what works work for me. Also, I am not affiliated with any of the above mentioned companies. I have long used Zpacks products though and as mentioned they just work for me, and many others I personally know.)