If you are aiming for say G5, don't worry about completing lower grades, it's a waste of materials and has no benefit, as soon as it lets you move onto the next grade roll then do so. At the end, you may be just a few percent off completing 100% G5, and those greedy engineers can force you to do quite a few rolls to get there, and the G5 rolls use high grade mats also, so many cmdrs don't bother with those last rolls as the end benefits are mostly miniscule, unless of course you are an ocd min-maxer and can't help yourself!