In (5.1), so is a place-holder for the VP make up words (in an inverted sentence),  and (5.2) tacitly contains a final predicate something like under amount x of pressure, where that amount x needs to be related to the (larger) amount of pressure experienced by Felix.  Interpreting ellipsis requires filling in of missing material; this can often be found at the surface level as a sequence of consecutive words (as in the gapping and bare ellipsis examples 2.5 and 2.6), but as seen in (5.1) and (5.2),  may instead (or in addition) require adaptation of the imported material to fit semantically into the new context. Further complications arise when the imported material contains referring expressions, as in the following variant of (5.2):