As a Beta Tester, I always had acceptable performance with the V1.2 LimeSDR operating from 10 MHz and up. All my testing was observational (non-scientific) and compared to other SDRs I owned (Red Pitaya and RTL-SDRs with upconversion). The videos I posted with the SDRConsole and GQRX apps running show the LimeSDR receiving on 20m (14 MHz). Performance of the V1.2 LimeSDR below 40m (7 MHz) was marginal and that's what inspired all the discussion in the July-August 2016 timeframe (when HF was just beginning to work on the LimeSDR) by the beta testers about changing the front end matching networks to improve the lower frequency (including HF Band) performance. Plus, there were schematic observations by others that the inputs were optimized for much higher frequencies (> 100 MHz) and they, too, wanted to see lower frequency performance improvement. When the curves were released by Ricardas, it appeared that we would get that better performance we were looking for from the LimeSDR, so I - like many others - were excited to see this happen. But thus far in the V1.4 boards, I'm not seeing that improvement. In fact, it just seems a weaker at 40m (7 MHz) than it did before, but I'm holding out hope that there are firmware adjustments coming to either be baselined with the V1.2 boards or better.
I am also of the opinion that if you publish specs for a product you have to live up to those claims as the manufacturer. Ultimately, the manufacturer of any product has to perform formal testing on their own to the specs they publish to be in compliance with their consumers. Beta Testers are there to play with the hardware and report the findings. The findings showed a deficiency in the lower frequencies (including the HF Band) and that was discussed. The curves were the solution to that issue by the manufacturer. What happened after that is anyone's guess.
Since I'm an experimenter by nature, it was always my intention that if I didn't get what I wanted out of the LimeSDR I was going to 'roll my own' to make it work. I may still do that, but right now I'm waiting to see if there will be firmware improvements that will finally set this radio right. One can only hope...
73 de Marty, KN0CK