I pasted the "Official" words from Deltran Corp (Battery Tender) I received last night...
"
Charles, You can hook positive to positive and negative to negative. We had to include the part about the chassis for UL purposes. Have a great day! XXXXXX XXXXX Customer Service Deltran Corp. 801 US HWY 92 East DeLand, FL 32724 (386) 736-7900"
I did the ring terminal hookups clamped under the 10mm nuts on the positive/negative terminals of the battery, routing the wire under the battery holddown clamp (making sure not to pinch the quick connect wiring). I electrical taped the fuse next to the positive ring terminal, and ran the line as ETYU did right along the drain channel under the hood (1st pic of #6 post on this thread - my vehicle is stored indoors as well)...on my 2000 SLK 230 the quick connect fits perfectly and can be extended out from the drain channel to where the quick connect plug has just enough room to pull the cap off and connect to the Battery Tender connection. I purchased the 25' lead extension because my Tender/electrical outlet is on the other side of the vehicle, I have an overhead rafter that I hang the extension from so that it falls directly over where the quick connect exits from the hood/windshield area (when I disconnect I simply loop the extension end through a wire tie attached further up the extension).
I used the heavy-duty velcro to keep the quick connect on the channel and also under the hood where the wire bends along side the drain channel so its taut enough to prevent the hood from contacting and cutting into it.
Again, thanx to y'all for the details and pics...that was sooo much easier to accomplish because of you!
Charlie