Bear in mind that the Tamiya Volac ESC was never updated, unlike the Hara Twister and a couple of the other KO based speedos.
Although the original version is a very good ESC the updated versions made some useful improvements.
I would advise you seek out a KO VFS-1 Competition 2 or a Hara Twister 2.2 as these are the latest version speedos. I'm not sure whether any of the other KO-based speedos (eg Yokomo/Corally) received the latest updates or not. Tamiya Volac may well be sold out and second hand only by now.