I'm getting a warning from Avast that the link is an attack page. Just so you know. JCAPS themselves may not know, if their site has been compromised by hackers to distribute malware.
In general, it isn't the brace part of a strut brace that's difficult, it's mounting the thing solidly to the shell. I've seen kits told you to mount them to the top of the wing round the strut using self-tappers . . . .
Googling for Unibrace gets me to
this bilingual English/Japanese site.
It looks very pretty, and is much more substantial and businesslike than the bits of pipe joining the strut tops that you usually see. I'd not like to try and fabricate something like this, not having aluminium casting capability in the shed.
You will have to pay premium prices for something like this, which is well designed but also made to look pretty. And it has to be shipped from California.
It's light, strong and rigid. If the attachment to the shell is done properly this will be a top-class piece of kit.
Attachment seems to be by
McMaster Nutserts, swage nuts that clamp to a hole drilled in sheet material in the same general way that pop-rivets do
And in searching I've found
this set of instructions from Unibrace. Attachment by four ½" nutserts and M8 bolts. That's substantial.
Searching also produces some endorsements from the VWVortex community.
One question I would ask, though, is whether it will fit the Leon shell? There are different versions specifically designed to fit the Mk.IV, V or VI Golf shells, and the shell shape is the one big difference between the Golf and Leon.