Well a slot adjustable pod was on use on the Epoch spec2 and I never had a problem with it. The Epoch was not fast tough, but washers could be used on the dNaNo to prevent slippage.
Another way would be an extender, basically a rigid rectangle with 4 holes, this one could be made in several length. The advantage is you can use the standard size T plates, stock, carbon, different hardness.
This is a Mini-z version of an extender I use with super long bodies.Works perfect.
I agree with Marc, making different length of T plates would be too much, especially if you want them soft, medium and hard.