I've taken quite a shine to this little mod, especially the building guide, which is a godsend for builders like me.
It does suffer from a set of issues though, which I'd like to address with a similar amount of suggestions.
First off, I like to build big, and when I say big, then I mean mega-massive. Sadly, turns out a spheroid as small as 128x128x20 can kill my semi-powerful gpu like it was nothing and leave it weeping, barely chugging along at 0,1-2 fps.
Alternatively, moving out of the shape makes it vanish, which is highly annoying in situation where you can't place blocks from the inside of the shape.
So, would it be at all possible to have the helper blocks only render when I'm within say... 10 blocks from them? This would also solve the problem of people using the block for aesthetics which you probably wanted to solve by introducing issue 3
Which is that there's no persistency to the block, it loses its settings when you move out of a certain range, which is kinda annoying when you have to go home for more materials, as a matter of fact, it'd be best if the block retained its settings, even after you breaking it. This issue is especially jarring when you're working on something big - 130 right clicks after every time you leave for a leak ain't fun, even if you're just holding the button.
And that in turn leads me to... Well, I'm strongly against GUI's, but this block really deserves one. Selecting sizes by typing them in would be amazing.
Since we're speaking of GUI's, there's two more settings which would help a builder greatly and I don't think selecting those would fit into the hold RMB schemata. The first is "even shapes". A simple button, which'd let you centre the shape off to the sides of the block would make this very easy to use indeed. Let's face it, using 4 building helpers next to each other for a modestly large, even cylinder could kill any computer. Let's not even get into how it's impossible to even set 'em up like that without a GUI. Oh man, and even spheres?
The second would be... semi-existing blocks. This would make the helper blocks similar to tall grass, in that you can right click a helper block, building block in hand to "replace" the helper block. This'd be exceedingly useful, especially for sky builds.
Hugs'n'kisses <3