Manhattan Trousers: Getting the Fit For Your Fabrication

Expecting a pair of pants to fit on first try is like playing the lotto and expecting to win the jackpot.  Mass production pants patterns are designed for one fabrication. If the fabrication changes then the fit process begins again. Modifications will be made based on different amounts of stretch and shrinkage.
So how do I ensure that the Manhattan Trouser pattern will work perfectly, with so many variables to factor in? My own delay in releasing a pants pattern was based on my struggles with fine tuning a fit that works for many different fabrications. For instance, I made a sample in which I had to go down a whole size based on the final Manhattan Trouser pattern because the fabric I chose had a decent amount of spandex vs the original draft for only mechanical stretch. I suppose there should be a formulation, but I am so not scientific and number crunching like that. Maybe there are those out there a little less daunted than me by the prospects of such an equation, but I will have to shy away.
Here is what I do: If I have enough of the final fabric I will make 2 pairs of pants, one a tester and one a final. Now I realize that this is not the most practical for most sewers and can be wasteful. Instead I would suggest making a muslin in a similar fabric. If you really want to skip a muslin size up if you are borderline. Cut out only the legs and baste together. Check the fit and determine if you need to slim it or expand it. Based on this modification, select your waistband and modify this piece as necessary and then cut out and test the same way that was done for the legs.
Pants are truly trial and error. Until you are familiar with the pattern keep an open mind and do a little extra work to make it work for you.