Double glazing may not be worth the extra expense and trouble.  Almost all commercial collectors are single glazed with high transmission tempered glass.
Double glazing is a two edged sword -- you reduce the heat losses out the glazing, but you also cut down on the light transmitted to the absorber.

As you say, for a DIY panel the hardest part is coming up with a good way to attach the risers to the fins.  The wiring the risers to the absorber plate is not going to work well.

Using copper fins soldered to copper risers is thermally efficient, but is expensive and labor intensive.

My 2 cents would be that the best of the DIY techniques is to form 6 to 8 inch wide aluminum sheet to the shape of the riser tube, and attach the alum sheets over the riser tubes with some silicone caulk between the two to improve heat transfer.  I think these would perfrom pretty well, and this techniques has been successfully used (see the Maine Solar link below).  There are some silicone caulks that have fillers to improve conductivity, but they are hard to buy in small quantity.

There are a couple fairly easy ways to form the sheet to fit the risers -- see links below.

Another option is to buy the absorber plates premade, and build the rest yourself.

Absorber plates using Maine Solar technique:
http://www.builditsolar.com/Projects/WaterHeating/MSClosedLoop.pdf

My "press":
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/House.htm
(this was for heat spreader plates, but same idea)

Another alternative is to use the extruded heat spreader plates that are sold for radiant floors -- these are pricey, but snap on the pipe with zero effort:
http://www.builditsolar.com/Experimental/CPVCCollector/cpvccollector.htm

This is the collector I built into my garden shed wall that uses premade absorber plates:
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/collectors.htm
By integrating the wall and collector you can save some money -- the net cost of the collector was only $8 per sqft (may be more now with current copper prices).

Some more ideas here:
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm

Just as a final thought, have you thought about making some or all of the collectors be air heaters instead of water heaters?  These are a ton easier and cheaper to build.  The downside is that there is no easy way to store the heat, but until you have quite a bit of collector area, storage is not really an issue -- you get some storage for free as the thermal mass or your house heats up.