I have to agree with Bruce on this one.
The volume of atomized material entering the combustion chamber does not change with any change of oil content. By far most of what is being compressed is air as alcohol and nitromethane are nearly as uncrompressible as oil. Any change do to simple crompression would be negligable.
The oil content itself however being less combustible may tend to pool somewhat into any gaps between the piston and cylinder wall.
That said any increase in compression would be minor and indeed offset to some degree by introducing a less combustible mixture which in itself would even out any performance increase.
If you are having compression problems it may be time for a rebuild or replacement.