[TowerTalk] converting a 10 meter monobander to 20

[Blair S Balden]

Hello towertalk ops!

I have a Cushcraft 10-4CD 4-element monobander.  Given current conditions on 10, I'm thinking about modifying it to work on 20 meters instead.  I figure adding loading coils into each element would do the trick.  I could start winding some and trying them, but I would like to start out with something close to right.  Would any of you be able to provide me with some guidance as to what coil diameter / number of turns / type of conductor would be appropriate and/or how to calculate same?   I run 100 watts of power.  

Would it be better to load it near the center of each element, the middle, or toward the ends?  It would be great if the thing could cover the entire band with a reasonable SWR, but even half the band would be OK.   

Also, I'm sure element spacing would be an issue.  I suppose I could go from 4 elements down to 3 (or even 2), if it makes sense.  The boom is about 16 feet long. 

Any tips or advice would be appreciated!

Blair, NP2F