Grid design query

[zinaphile]

I have a 15x15 puzzle aimed at a Wed difficulty (NYT standards). Fourth column in from the NE and SW corners I have 4 blocks lined up vertically, leading to a stack of 4 three letter words, each going across.  A 2 or 3 high stack like this is pretty common, but I don't recall seeing a stack of 4. Is this in some way taboo? Trying to figure out how hard to work on getting a different grid design to work - no luck so far.
 
FWIW - crossing these stacks are two 9's and a 5.  Overall I have 39 total blocks, 72 words, 5.17 mean length.   

[mmcbs]

Seems like a high block count for a 72 word grid. There's no "rule" about a line of 4 blocks, however. If you'd be interested in having another set of eyes look at it, shoot me an email with the grid and your theme entry letter counts. McClain.salem@gmail.com.