....if you don't get that 1/4"seam allowance automatically as you are piecing it then means your 1/4" seam is either too thick to too skimpy....I personally would NOT trim to 1/8" if that's all you have...that's a sure way to get a raveled seam after washing...not enough fabric their to hold that seam together.....
Ugly four letter----REDO - saves lots of misery in the end...jmho