To address both @Michael McKelvey and @James, as you're both talking about different aspects of these switches, Yes, you can wire both of them to light a dash lamp if one of the brake fluid circuits fails. As James said, the wiring is a bit tricky but not too much so (The Bentley Service Manual wiring diagram for a 1970 Beetle shows how they work), but I have yet to see a Speedster/Spyder wired up that way with a working dash light.
OTOH, it makes sense to wire both switches in parallel (slightly different wiring) so that when one fails (it certainly will) the other one will just keep working until IT fails, too. But then it's important to swap out BOTH switches if you lose your brake lights because both switches will be bad at that point. Info I get from the Hot Rod crowd is that these Asian hydraulic switches seem to have a life of around 18 - 24 months, which really sucks for something like that.
Or you could just upgrade to a mechanical switch in the cockpit and put this all behind you.
BTW, Mike - I remember (I think) that you had tried some LED lights from "SuperBright". I just got a pair of 921 LED bulbs for my 3'rd brake light from them (arrived today) and HOLY CARP! Are those things ever BRIGHT! Practically light up the whole shop! Another satisfied customer......