I'm sorry to hear about Chuck. He had a huge impact on my life.
Back in 1987 I was a senior in high school. My family had a computer store and we were selling PC clones (Leading Edge), and most people could only afford monochrome monitors.
The problem was, most "fun" software (games, Print Shop, etc) required a CGA card and color monitor. I found Chuck's program, Sim-CGA, on a download site. It was a TSR that emulated a CGA card using a Hercules monochome adapter.
I called up Chuck - his phone number came with the software! - and asked if he'd like to go into business selling it. What must he have thought getting a call from some young 17-year-old?!
He said "How about we go 50-50?" and my company (Excelsior Software) was born. Chuck kept improving Sim-CGA over the freeware version. I worked on all the packaging, sales, and distribution. We had the #1 selling PC ultility in the country for almost a year.
I was copying all the floppies myself in my parent's store. At one point I suggested to Chuck "Can't we make copying quicker by reading the disk image into memory and just writing it over and over?" After maybe a weekend Chuck sent me a new program he wrote called "Copy QM" (Copy Quick/Multiple) which did exactly that. What an improvement!
Chuck knew hardware cold. He was an amazing developer. I was already on a course to go to college for Comp Sci, and Chuck was a great role model.
When I saw companies like Quaterdeck selling an Expanded Memory Emulator (PC's came with "Extended Memory", EMS was a different standard) I mentioned it to Chuck. He wrote his own EMS emulator which we sold as "Sim-EMS" for only $24.95.
Sim-CGA and Sim-EMS helped me pay my way through college (plus working weekends and summers in my parents' Software City).
At one point, Chuck told me he went to college at Purdue. He strongly suggested I look at U Penn for Comp Sci, but I had to stay closer to home (Univ of Scranton) because of my family's store.
However, I never forgot about Purdue. If it could produce a Chuck Guzis, it must be a great school.
Fast forward ~5 years ago when my younder daugher was looking at colleges. I remembered Chuck & Purdue and we went to check it out. She wound up attending as a double (honors) major in Comp Sci and Data Science. After a great college experience, she is starting her first job (at Nvidia!) this February. If it weren't for Chuck, we never would have even looked at Purdue.
We fell out of touch over the years after he moved, but I did try (unsuccessfully) to re-connect when my younger daughter started college. I'm sorry I couldn't tell him about the continued positive impact he had on my life.
One other quick story: Chuck impressed upon me that knowing the hardware was just as important as the software (he's probably why I've also branched off into collecting and restoring old computers, pinball, and arcade machines). I had an Atari ST once and was complaining to Chuck about how expensive hard drives were. He reverse-enginereed his own SCSI adapter and wrote his own driver software and sent me one. It seemed like there was nothing he couldn't do if we put his mind to it.