Just did the same thing this past weekend except I chose the "Crystal" Clear tail light. I also chose to keep the faster paced turn signals...more annoying...almost strobe like.(Shibumi @ Dec. 31 2006,19:21) This is what you get by just cutting off the shovel and getting a Clear Alternatives integrated turn signal LED unit off eBay for about $89. Much cleaner than stock, if you want more a new undertail will run $200-300.
Use a dremmel for cutting and sanding to make it easy.
Also, with all the chain grease and road grime that gets thrown underneath the tail I would be cleaning the inside of the undertail w/ WD-40 after every ride.
I'll be gettinga hugger sometime this year.