DVC 4 ohm sub wiring?

I read your post a little differently:  your friend is telling you to use one of the voice coils, but "cancelling out" the other coil by connecting the terminals together is not necessary.  It is simply not used at all and the terminals would be left alone.  That would certainly maintain the 4 ohm load you're looking for but you have to keep in mind that since only one coil would be functioning the overall power capacity of the subwoofer would be cut in half.  A much better solution is to wire the coils in series for a total 8 ohm load as haemphyst suggested and bridge that load onto the amp. 

Not knowing the specs of either the sub or the amp, a guess would be that using only one coil will be a mismatch in power rating with the amp running to a bridged load.  Do this test:  look at the power rating of the sub and divide it in half (use RMS only).  Look at the bridged power rating of the amp, is it more than that or less?  If it is more, which it probably is, don't use just one coil.  Although the MINIMUM load on an amp can be 4 ohms, it doesn't have to be wired that way.  Use it at 8 ohms and you'll probably find it to be suitable until such time as you can trade out your sub for one that matches better (...if "better" means maximum power output...) with the two-channel amp such as a SVC 4, DVC 8 or a DVC 2.

Wiring Wizard