I am looking for how many yards are needed to do a larger Monster Maroon. I’m sure others here have had to custom tailor above the 2xl standard pattern and would know how much is needed. Also, how did you make the modifications to fit the higher sizes?
Here is a simple explanation. If you look at one element of your multiple size pattern such as “chest”, it should give a range of sizes and measurements. One example might be XL has a chest measurement of 46-48 inches and XXL has the chest as 50-52 inches. The next larger size even in the pattern does not provide for it would be XXXL with an estimated chest measure of 54-56 inches. If your garment has two pieces to cover “the chest” such as the front and back pieces of a t-shirt, the completed garment would need to increase approximately 2 inches in total, 1 inch for each piece, or ½ inch on each of the left and right sides of both the 'front” and “back” pieces of the pattern. So the fabric for both the left and right XXXL pieces will each be 1 inch wider than the XXL size. The length of the pieces do not increase as much but will depend upon the height of the individual. Many patterns have explicit areas where the length of a patterns can be lengthen or shorten as needed. Note if the garment has three pieces to cover the chest, such as a jacket with an overlap, or four pieces because the the front and back each requires two pieces to provide a more tailored fit, this 2” increase must be distributed, as needed among all the pieces.
To enlarge the pattern pieces you need to address each body measurement individually but in a similar manner.
To obtain the required yardage, the best approach would be to first create new larger pattern pieces for the garment and then use them to produce a layout based on the width of the fabric to be used. Also if it is necessary to match design elements of the fabric or be concerned with the grain or nap of the fabric, these consideration need to be taken into account when making your layout.
Once you have your new pattern I would recommend making a sample of your garment out of cheaper, but similar weight fabric to test your layout, pattern pieces, and construction details.