Having said all that above....here is an alternative.
Draw a diagram on graft paper of the top of the bed. Twin is 39"x78" or there about.
If you take 20" off top for pillow then you have 39"x58" area for the design.
If you leave about 6" on either side then you have a circle of 27". Balance the center.
Assuming this then.
Try to find some kind of measuring stick that has holes in it that you can use like a compas.
If not then bore holes in a wooden yardstick at each 1" or even 1/2". Use this to draw your circles.
Make one template for the curved ends.........and you have it redrawn to the size you need. Work on only 1/2 of the design and flip for mirrow image. Draw the verticle stem in the lower center. This will define the size of the other channels. Does this make sense and help? All you need is ruler or straight edge of about 18" to use as a compas.

I use EQ7, but I'm pretty sure you can enlarge on Excel as well. I've seen a tutorial somewhere...on this board maybe?

My concern with having a printer enlarge is that the image might get distored in the repeated enlargments. If 1/2 of the design is used and is originally on an 8x10 paper then it will be about 4" It might take three or four enlargments after that to get the 1/2 to around 12", 13" or 14" needed. As the printed if it is possible.

I'm not sure what you're saying, but I've never had a problem. I enlarge to the size I want only 1 time (maintaining "aspect ratio") and it prints on as many sheets as it needs for that size. After printing, you just tape the pages together and voila!

yes enlarge 1/4 of it only. then make more copies and paste together. looks like a great idea for a quilt!

I can see this being a problem if you're using a photocopier to enlarge your design, especially if you end up using different copiers, because they all enlarge at slightly different rates. But this should not be an issue if you're simply printing from a file.

Here's how I enlarged my design. I scanned my photo, imported it into EQ, then used the "trace" feature and traced the lines. I saved it onto a thumb drive, took it into Kinko's, and told them how large I wanted it. The Kinko's employee did the computer work needed to get it oriented and sized correctly, and it printed on a printer that uses 36" wide paper on a roll, so it prints however long you need it. The size I requested was easily printed with just one pass, but if I had needed it wider than 36", the employee would have divided the image in half, printed out both halves, and then I would have just taped or glued it together.

The whole project ended up costing me only $10, which I thought very reasonable.