Hi Paul,
Yes, I can comment. I bought a set of these heads a little over a year ago but have yet to install them due to an intermittent problem with my machine. I can tell you they are very well made and I can vouch for Colin. He is a stand up guy to do business with. Talks a little funny!
I hope to install these soon and if you like I can then come back and do a write up.....or what ever it is called!
Mike
ps if you want to see how strong they are, watch the video of the carving of the pineapple!