
Then get a 3/4" x 3/4" or 1/2" x 1/2" timber square around 8' long and tack it with fine nails (or staple) to the plywood along the plate curve. This should get you around half a plate cut in one go.
Next, put one of these

into the router and set the roller to run on the timber square and begin trimming the plate


When you come to move the timber for the next cut, just make sure that there is at least a foot of overlap into the section you've just cut to ensure that you keep to the correct line.
Hope this makes life a little easier for someone as I have found it far easier (and far more accurate) than trimming down using a plane

Cheers......Nick
PS: If anyone needs a sketch, just shout
