VCC and ground aren’t the problem, as @Ashley_M_Kirchner_No notes, it’s easy enough to solder them into the second set of pads (on the underside, even.) The problem is that when you cut the strip, you’re necessarily cutting the data pad in half and it’s not much more than 2mm diameter to start with.
Another difficulty I’ve come up against is when shrinking the heat shrink over the end of the silicon tube it’s hard to heat it evenly (using a jet-flame lighter, maybe that’s my problem?) and it comes out all kinked and doesn’t stay in place.
I’m away for a few days but when I get back I think my strategy is going to be to sacrifice the end LED, solder to the bottom of the strip, and use a couple of short lengths of the tinned copper braid I just bought as the power “bus”, meaning I can run the power wires in a straight line down to the bus, instead of kinking and stressing them by trying to connect them straight to the main power cable. Fold the whole lot into a strip of gaffer tape for insulation.