At the moment, your proposed approach is the only possible way to specify different size distributions. I can see what you mean about cumbersome. Do you really have 80 different potential size distributions for each management type or could some of the strata be aggregated to have the same size distribution? For example could you take a management type and split it up into a few different size categories like small partial cut applied to strata x, y, z; medium partial cut applied to strata r, s, t; etc…
In future this is a modification we could consider for Path – allowing the size distribution to be specified by stratum.