I've been having fun with my V6 uBITX on the air while I'm waiting on some revised prototype boards to arrive from China. I'm mainly a CW op and and that usually works best QRP anyway.
Worked K9CT on 40 a couple days ago (got him first call), W3R on 20 yesterday (again, first call) and just a few minutes ago worked W1VE on 20 meters.
My antenna is an end fed Zepp QRP antenna (PAR EndFedZ) and it's only 15 feet off the ground plus it's only about 3 feet above the roof of my house. I use it mainly for testing when I'm working on things like the uBITX.
I was also using our TSW Teensy 4.0 to NANO plug in adapter on the Factory supplied V6 Raduino. For the CW ops out there having problems with the keyer timing in the stock firmware, you might consider changing over to the Teensy 4.0 and our latest firmware (available from TSW) as the keyer operates like it should with decent timing. TX starts immediately on the first character element and if you set CW Delay to 200-250 milliseconds, it comes back to RX fast enough that you don't lose the other guys first character.
All the details are on the TSW website - www.w0eb.com . Using the adapter, you might have to bend the 7805 regulator slightly toward the bottom of the factory V6 Raduino in order for the bottom edge to clear the heat sink on the 7805 (Factory has it a bit too close to the NANO socket).
I've been running the rig on the air configured like this for quite some time now and have run into no issues at all regarding the Teensy 4 replacing the NANO as the CPU. Nice thing is the Teensy 4.0's available program space is only 2 percent full whereas the NANO with current software is around 90 percent full. Add much more to the NANO's program and there won't be enough room for the program to operate properly.
Some people are balking at the $19.95 price of the Teensy 4.0 but yet they are willing to spend quite a bit more than that for the NEXTION display which won't fit the mounting holes of the factory case (so they have to modify it anyway) and also the NEXTION's connections are not really "plug and play" either.
Using the Teensy 4.0 to NANO adapter is about as close to plug and play as you can get except for the need to use a separate key jack for the paddles. If you don't use the keyer, and just use a hand key or plug in an external keyer you can use the PTT contacts on the microphone connector and you don't have to modify your pretty case.
No matter what you do there are going to be compromises that will have to be made if you want to really speed up the display and allow for the ILI9341's available font libraries to be used.
We've kept the screen close to what was original with a few useful additions and ours doesn't take 3-4 seconds to paint the display. Also ours doesn't repaint the entire display every time you change something and doesn't "blink" when tuning or touching an on-screen button. This is one of the real advantages of a 600 MHz processor vs the MUCH slower NANO.
Just food for thought ----
TSW Project Coordinator