Mine are both set up with the minimum height - and despite riding for the last 7 years on road and off I haven’t found grounding to be an issue. They are designed to take the occasional hit anyway. One of the Czech manufacturers says that if the paint on the bottom hasn’t been rubbed off, then you’re neglecting it!
I got my Racemax a year after the Trexx (which was my first). It’s really good for longer stuff and you do get a bit more mph with the bigger wheels. I bought it as a frame only because, as a cyclist of many years, I had most of the necessary components anyway.
Along the way I also picked up an ex-demo Yedoo Dragstr (20/20 like your Kostka) which is ridiculously light yet very capable off road with some fat tyres.