Well why buy the skip white dist anyhow if your engine runs good? Buy the vac advance kit and give it to a bud that needs it,,,it's XMAS after all
The best part of the kit may be the vac adv limiter plate if it has one, that is the best 4 bucks you could ever spend. It is more important than the adjustable can imo. typically the can adjustments can vary the actuation of the advance by only a few "hg of engine vac.
Your motor pulls 15 "hg vacuum is that at idle what about cruise?, most adjustable cans cannot be adjusted above about 12 "hg. At 15"wg the vacuum advance will be all in no matter how you adjust the set screw. But if your motor pulls say 11" hg at idle or 8-10"hg at cruse RPM lets say then you can make better use of the adjustable can cause you can still adjust it within those vacuum levels.
take it for a spin with the vacuum gage connected and record whats going on,,,it will help you spend your money or not