And they didn't have just any client. They had a former NHL player.
The 28-year-old, who now works in scouting for the Arizona Coyotes, played 63 games in five NHL seasons as a forward with the Coyotes and Boston Bruins before his career ended.
"We wanted him to feel the ice," Harsch said. "The No. 1 piece of this is he's comfortable in his prosthesis. No. 2, we had to look at suspension. We needed to make sure that this thing was well suspended and connected to his limb, as much of an intimate feel as you could ever have."
There still are tweaks to be made to the skate, in an effort to ensure as much movement as possible while taking as much weight as possible off of the limb. They want to make sure the steel plate is durable, that it's not going to shatter if a puck hits it, that it's light. There are cosmetic fixes to be made too. But as they perfect Cunningham's skate, Harsch is confident they'll be able to use what they learned to make skates for other amputees, to share the knowledge.
"We looked at the demands of ice hockey and the movements, the forces and moments, and what we need this prosthesis and this skate to do," Harsch said. "We started studying the demands of the sport and came up with a prototype that's working out really well so far. That's what you saw yesterday.
"I think he'd probably tell you that was a gamechanger."
Cunningham still is working through his recovery. He said for a while it was "a lot of two steps forward, three steps back," but that it has been moving in the right direction.
"Now that I've got some stability in my leg and I'm not getting the pinpoint pressures anymore, it's made a huge difference," he said. "I'm back to regular life, really. The only thing that's different now is I don't play hockey anymore. But everything else is the same."
There is a golf trip next week. He can play 18 holes. He ran three miles on Thursday.
"Trying to live as normal as possible," Cunningham said. "Obviously some pressure points and pain at some points, but really no restrictions. They really say an active life goes on, and that's where I'm at right now, just tiptoeing my way to get to where I want to be."
Cunningham admits social media isn't exactly his thing. So when his Instagram post of him skating went viral on Wednesday -- with 10,000-plus likes and nearly 500 comments -- he was surprised. He didn't realize what the response might be.
But he was glad to be able to share, even the missteps, like when he attempted to skate backward at the end of the clip.
"Being an amputee is not the easiest thing in the world and it takes a lot of people some time to build up the confidence to try new things," Cunningham said. "I got a text, it was like, 'Why didn't you edit (out) you skating backwards like that?' I wanted to show that I still struggle to do things too, and it's all trial and error. That's why I left it."
And then he joked, "A good buddy of mine texted me, 'You could never skate backwards anyway.'"
Cunningham reflected that the prosthetics industry has come a long way in the past couple of decades. As he put it, "Twenty years ago, I would have lost this thing and they would have put a wood peg in there and I'd be walking around on it, not being able to do anything."
But companies like Peter Harsch Prosthetics have revolutionized the industry, and organizations like the Challenged Athletes Foundation have helped with grants and access and connection. Each has been instrumental in getting Cunningham to this point, where he can step onto the ice and then share his progress with the world.
"It feels good," he said. "Obviously went through some times when I didn't know if I was ever going to be able to do anything. So I think it's just another step in the process of moving forward and getting healthy.
"I think I'm trying to take the mindset of don't look back, just only look forward. This is the card you're dealt and if you want to play the deck you've got to deal with everything and move on. That's been a tougher part, but as I get healthier, as I get more mobile, it gets easier."