Not sure if I understood the probl.. Anyway: when you turn a polygon patch in a subpatch points act as 'attractors' for vertices (the approx is usually due to the equation's exponent). Pratically one way to control it is to change the weight for every single point of your mesh. By default weight is set to 0 but if you select 'subpatch weight' in the low right corner of modeler and pick the weight tool you can change this value (you can do it in the info window too); when is set to 100 the vertex and controlpoint share the same position in the space so if you change all values of a subpathed mesh to 100 you won't have any difference in shape between the polygonal cage and your mesh (basically you can hit 'tab' without affecting the mesh). This is not so useful but the 'in between' can be used to match polygonal edges with subpathed edges, to change bones influence, to change shader properties and a like. Here is an example where I combined subpatches with polys in a 'easy to draw in 2D shape' but 'painful to model in 3D shape'
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