Make
real good friends with your seam ripper.
Where abouts in the process are the problems showing up? Is it putting the first 2 hst's together or when you put 2 pairs of hst's together? Sometimes it doesn't show up that things are fractionally out on the first pair of hst's until you stitch them to the second pair.
First check that all of your seam allowances are going in the same direction (clockwise or anticlockwise - doesn't matter which just all the same)
Either way you don't necessarily need to rip the whole seam, just about 1/3 to 1/2 of it nearest to the points that aren't matching up, take careful note of which way they need to shuffle to be matched (pinning either side of the seam at this point can be useful, but
I don't always do so because sometimes it works for me and sometimes it doesn't
) then machine just the bare 1/2" across the junction. take it out and check, if they are ok then it is good to re-stitch the whole length, if it isn't then you only have 1/2" to rip. (and if you haven't ripped the whole length of the seam then the ends are still 'tethered' which makes things simpler)
Have you checked out the Classrooms - Laura Nownes did a set of lessons for a sampler quilt and she shows how to do pinwheels on there.[url]learn/classrooms/[/url]
Alternatively instead of pressing your seams to one side you could try pressing them open. You might find this way easier. Whatever you do there is still a lot of bulk to deal with and you need to be vigorous with the pressing.