Or ...Exactly.
When I engineer something I always do it to Grade 5 (except Life Support - I'm not going to Colonia to get THAT G5) so I always make sure I have enough mats to roll for each grade i.e.:
G1 = 2 rolls
G2 = 4 rolls
G3 = 6 rolls
G4 = 8 rolls
G5 = 10 rolls
This way each module I engineer is guaranteed to be 100% G5.
As Ian pointed out above, for about 90% less effort, you could max out the G4 level and usually have something 90+% as good as fully G5. And even if you must have that G5 cachet, the rolls needed to go from halfway complete to maxed out G5 are purely a tax on obsessive behavior. Just don't do it if you even slightly value your time!