Several regular posters here have tried this over the past two years. It's perfectly legal.
But as Scotus alluded to above, if you don't up the tension hugely you will get an uncontrollable stringbed. First of all, in order to avoid frame distortion you must almost double the tension of the crosses as compared to the mains, as there are now half as many crosses as the frame was designed for. Wilson re-engineered their Spin Effect racquets so that you don't have to do that.
So then, let's say you're using a stiffer copoly string and you're now at 40# on the mains and 70# on the crosses. Unfortunately, that's no good because the low tension mains will slide way too far sideways and not be able to snap back in time to produce the extra spin you'd be looking for with a pattern like this. When the main strings slide but fail to snap back into line quick enough, you get a very high rebound angle but terrible spin. So your ball will fly high over the net and deep, but it won't have that extra spin that would make it dive back down in front of the baseline. In addition, the rebound angle will vary greatly from shot to shot, making it very difficult to control.
The remedy some of us have used is kevlar mains. Kevlar strings are more than twice as stiff as copoly, so even tensioned at 40# they will be stiffer than the copoly crosses tensioned at 70#. Now, the stiff kevlar mains will slide less and snap back with more energy, producing the spin you're after. But even still, you might find this setup lacking in control, so then you'd want to up the tensions further, and at that point you'd be looking for a very thick poly that can handle 80+ pounds of tension. At that point, you might wonder why you didn't just pick up a Steam. But I encourage you to try it out if you've got some kevlar and thick poly strings laying around.
If you want to read about others' experiments with these patterns, just do a search for "16x10" or "18x11"