Sam,I suppose you are creating your tremolos as half note tremolos, e. g. two 8th notes with open noteheads (half note noteheads). The general solution is to create the tremolo as a tuplet (e. g. two 8ths in the space of a half note). You can hide the ratio and the bracket of the tuplet. And you can use the Note Shape Tool to change the noteheads to half note noteheads (I think that the half note notehead is in slot 250 in the Maestro font). You can use the Beam Extension Tool to make the beams shorter so that they don't touch the stem.
Having too many beats in a measure is also possible. Just change the time signature for that measure and add as many beats as you like. Before doing anything else in the Time Signature dialog box you might like to click on More Choices and check Use a Different Time Signature for Display.
Ask again if this doesn't solve your problems.
Have fun
Peter
