If you mean modifying goggles into a hybrid - then my advice is not to do soI'm thinking of combining a I4 and pro/ E flex, have any of you got some tips for this?
A modified goggle will no longer be an approved set of goggles
If you mean attaching part of the e/flex - EG sticking the 'skirt' chin area onto the bottom of i4s for more face cover then you could - but why?
If the i4 goggles are too small for your face then consider the i3