Custon CPU cooling question

I'vew got a plan drawn up in my mind for a heatsink for my next build of my computer, but in order for it to work I will have to cut the heatsink in half vertically. The cut will ruin accross the CPU core as well. My question is, will the cut in half matter as far as heat transfer goes, or will it work the same? Also, will it work better with the two sides placed together with a thermal compound, or bare metal? Would a soldered joint be a good way to put them back together, or is there danger of the CPU temperature loosening the solder? 63/37 solder of course. I intend to use copper for the heatsink, but may use aluminum if that makes a difference in the answers of my questions.