Pruning a blue spruce shrub?

I know in general spruces and pines don't like to be pruned very much. Not big prunings anyway, like you can do with maples. So the question is how much is too much when it comes to pruning back a blue spruce shrub to keep the size in check?

I have 2 - 10 year old (approx) Picea pungens that are less than 40 inches tall, one at my home & one at my business. The foliage is pruned so it is a perfectly flat circle sitting atop the trunk. It is growing so flat & so densely that I can place a drinking glass filled with water on it. To better imagine the appearance, think of a wagon wheel on top of a trunk. The foliage is less than the depth (when situated horizontally) of a wagon wheel (less than 3 inches total) and the diameter is approximately the same. Another way to picture it is imagine a giant Frisbee with the Frisbee being the foliage. Set it on a trunk & you've got the picture.

Al

Generally accepted rule of thumb is to never remove more than 1/3 of the foliage.
Personally, I think many say you shouldn't pruned spruces and pines because they feel it's wrong to alter the natural shape. A spruce can be pruned in such a way to retain that layered branching look as opposed to just shearing and ending up with a dense solid looking shape. One of the first things you can do to keep it in check is snap off the candles in the spring. (that's the new growth that emerges from the ends)

How much? I've got a 15 -18' spruce that wasn't a true 'Blue' and last April I decided it had to go. It had already been limbed up a couple of times to about 3'. One day I went and cut off all branches as high as I could reach without a ladder then got the pole saw and lopped off the leader. (It was raining) After getting all the branches cut up and staged for trash pick up next day I was sitting there looking at it and it reminded me of a Palm tree. ??? I decided to keep it if it lived. It did! I refer to it as my "Arctic Palm" and a number of visitors have initially thought it was. You don't notice it at first unless you look up. I'll try to remember to post a pic tonight. I have a stand of other spruces out back that are just now really starting to grow (they were started from seed) and are about 6' and spreading out. I'm going to train all of these in the same fashion and have a stand of Palm trees.

You can prune very heavily as long as you water but it's safest to do late winter or early spring.

I asked this question because someone asked me and I thought it wasn't a good idea to prune too much on a spruce shrub. I think they've never pruned it regularly and now want to really whack it back....but I was thinking that would not be a good idea since it probably wouldn't shoot out new growth like a maple would or something similar. I guess this wouldn't be a problem if it was pruned every year...but my impression is that it's never been done and now they want to.

If the prune back to limbs without needles it's most likely a goner. Sounds like they should transplant this to a better area.

my 'Arctic Palm'