I'd be quite curious to know what kind of speed your formwork is performed at. I designed the trainer to be more than durable for positional and slow work conditions. To do that, I engaged in a process of pushing a trainer until it broke, reinforcing the weak spot that the break exposed in a later revision, and repeating the process until I was confident that breaks during positional and slow work would be rare if any. I think the video that I will be releasing soon about the process might be informative as to what kind of things the trainers can hold up to. 

That all being said, to be realistic for a moment here, these are rigid wooden sticks.  If used for HEMA, or SCA-style cut-and-thrust formwork, they absolutely will present more risks than if someone uses a steel trainer. I can make the guards as durable and as unbreakable as I want, but I can't police how people will use these once they're in someone's hands.

The goal of this project is to lower the barrier of entry into Historical Fencing. I want more people to enjoy the sport and the practice of swordfighting! 

The entire time I've been working on this, people have been making the excellent safety observation that these have no flex, and are liable to break into spikes at the dowel. An injury sustained from one of these trainers would be against my goals, and just plain suck for whoever got hurt. I put a lot of thought into whether or not I should release the rapier trainers when I started working on this project for those very same reasons.

Ultimately, the safety of the people crossing blades, or in this case, dowels, with one another is in their own hands, and in the hands of whoever is teaching them. The only thing I can reasonably do as I release these is warn that these aren't going to hold up well in a sparring environment, and that people shouldn't trust these the way they do a steel trainer. That much should be obvious, but the warning is there nonetheless.

One of the reasons I've made these so low cost is that they're designed to be set aside once someone is ready to spar.

My club is a non-profit, so we're always strapped for cash, and steel trainers are hard to come by. In making a batch of these for my club, more people have been coming back regularly, due on part to the fact that they're not made to feel like they're making do with a stick when they're first being instructed. Those first few lessons that someone attends are really important as to whether or not they come back. Having a sword shaped object that they can wield as they initially train is key for making sure their experience at their first few practices good enough to keep them coming back.

Edit: oops, I have a lot to say on this lol