Hi, No. 1 Son UK,
That's a much better place to attach it, and would certainly solve one of my gripes. Yours sounds a much more useful piece of kit, with a proper vice on it. I got mine new when I bought my lathe (same as yours, with a different badge) from Warco, and was a bit irked to find that, to get a secure mounting so it would straddle the centre-line, I would need to start drilling and tapping the cross-slide, rather than just bolting the thing down. My lathe was new, and I wanted to keep it original until the warranty ran out. As roconner's mini-lathe also comes from Warco, who I believe still advertise the same vertical slide as an accessory for it, I just wanted to warn him that it has its limitations in case he was thinking of ordering the same thing from them.
As you say, a vertical slide on a lathe is always going to be rather limited in the range of work it can handle by comparison to a mini-mill (or even a micro-mill).
Andy