Hi, sorry I get into this a bit late

There is evidence for front laced kirtle with seams curving over the bust for ca. 1450, have a look:
http://www.artbible.info/art/large/601.html. So your pattern should be ok.
I take it your pattern has a front, back and two side parts (left and right), or is it 6 panels?
Are you using a bought pattern, or is it fitted to your body block? If it is a bought pattern you might want to check the fit of the pattern by cutting it in a cheap material and machining the seams, if you want to make sure it looks good before putting all the effort in.
If you want more fullness at the bottom, you could always insert triangular gores into the seams. As you can see in the picture of the Virgin and child from the link above the upper part of the kirtle should be fitted tightly to the body, it supports the bust (and can give a nice lift to it as well

) and the tight fit around the ribcage makes sure the dress does not ride up when you pull the skirt up. If you have the book, look at the section in Katrin Kania's Kleidung im Mittelalter (p.161ff.)
What material are you using? Seam-and-fell is a classic linen seam, but very work intensive (especially in case you haven't done it regularly). If you are using a material that frays rather easily you could also use a run-and-fell seam, just make sure you use a backstitch every couple of stitches instead of a running stitch to stop it from being pulled. If you are using a denser wool, you could use a an overlapping hemming stitch (Sarah Thursfield refers to it as Lapping a seam, MTA p. 45) It has been found on extant garments, where the overlap is only 0.5cm. This creates a flat seam, whereas run-and-fell or seam-and-fell get more bulky. If you are using linen, definitely use the seam-and-fell seam, it gives a nice flat and very sturdy seam especially if you flatten the oversewn seam down before hemming down the other side.
I'm still looking for evidence depicting short sleeves for English women's kirtles in the 2nd half of the 15th century. If you have one, I'd love to have the source, it would save me hours of more search! Most pictures I have seen so far show long sleeves that could possibly be rolled up (buttoned or laced sleeve). I know, there is the women in the blue kirtles in the month of June in the Tres Riches Heures, but it's Northern France, and 1st half of the 15th century.
Hope this helps, and I haven't bored you

Best wishes, and let us know how you get on
Christine