The middle of the middle levels - by definition - is complementary with itself. This means in effect that it is the least complementary (i.e. the most differentiated) of all levels.

Therefore when development becomes very specialised at L0,H0 (formal), this tends to limit (sometimes severely) the possibility of healthy dynamic links with other levels.

Of course in practice complete specialisation does not take place so that both prepersonal and transpersonal (reflecting the understanding of other stages) will be also to a degree experienced.
However it is still true that in practice very little sustained development of “high” levels takes place in our culture.

Ultimately what is most and what is least are complementary. This entails that L0,H0 is ultimately complementary with the “highest” (and “lowest”) levels of nondual contemplative awareness. In other words, the greatest degree of integration requires in turn the greatest degree of differentiation (and vice versa).

However this entails that a very advanced degree of nondual awareness is required to properly integrate specialised development in dualistic type appreciation.

And because such specialisation can greatly hinder the possibility of contemplative awareness, we have a very real dilemma.

Thus though dualistic development is important, we have lost the balance in our culture with the need for corresponding nondual awareness.

So perhaps if we were to initially sacrifice undue specialisation in such development, the possibility for authentic spiritual development could thereby be enhanced.

With the two other middle levels L0 (concrete) and H0 (vision-logic) a degree of implicit complementary is entailed in that L0 and H0 - which in turn are partially related to the lower and higher levels respectively - are complementary with each other.