Adding the extra t-nut on the Z rail was a lifesaver. The original D300 guide has the wire guide for the whip only on the left (X-Z span) and with that orientation the heater cables were about an inch shot of the connectors. Moving the guide to right (Y-Z span) allowed everything to connect with no extensions.
Put some electical tape over the exposed contacts in the LED strip shown in the third photo. There 3 contact areas on each strip exclusing the ends. Might save yourself from a short or shock later on.
Another option here is to use an elastic therapy band.