zipper too long and trouble reading pattern
Yesterday I got a call from a friend who needs a Halloween costume by Friday morning (basically just a big loose sleeper suit). He was at JoAnns and he found the perfect pattern and fabric. His only problem - he doesn't sew. He asked if I could make it for him because I quilt. I looked at it on line and despite the fact that I do not know how to sew garments, I agreed to give it a shot. He purchased the pattern, fabric, and zipper and brought it all to my house. I cut out the pieces that I needed last night and tonight I plan to sew it up (wish me luck!). The main point is this doesn't need to be perfect or even close - it just has to cover his body. The pattern is easy, and I'm not sewing the gloves, tail, or hood. I put a link below so you can see it looks like a big sleeper suit.
1. The pattern calls for a 22" zipper, but my friend bought a 28" zipper. Should I cut the zipper at the top? Tuck the bottom 6" inside the body of the suit, or try to extend the zipper the full 28" (I'm afraid this may put the bottom of the zipper in the crotch of the suit, but if this is the easiest then I'll do it - doesn't need to be perfect). Any other zipper tips? I've never sewn one before. He is also willing to safety pin this closed if I can't figure out the zipper.
2. The pattern calls for bias tape around the collar. He didn't buy any. I'm not putting a hood on it. Does the bias tape just finish it off so it looks or feels nicer? Is there any reason I really need it? Or could I just cut some cotton on the bias and make my own?
3. The pattern says to hem 1" from the edge of the sleeves and at the bottom of the legs. Then in the directions when it gets to the part about finishing the edges it says "for easier insertion of elastic, baste about 3" of seam allowances in place at casing area." I have no idea what this means. The next step says "to form casing for elastic, turn in 3/4" on lower edge of sleeves and legs. Stitch, leaving an opening." This makes sense to me, but I wondered why I should hem all the pieces if I'm just going to go on to turn it under again to make a casing for the elastic. Won't this just add unnecessary bulk? And what do they mean by basting 3" of seam allowance?
Thanks for any advice/help!