I found that the macro in my FZ15 was the best with the zoom wide open. I can focus as close as things that are touching the lens!
With your zoom at wide angle, it's less prone to camera shake. Another thing that would make sharp macros is LIGHTING! You could use the flash, that is if the lens isn't so close that it blocks the light. Or I'd probably just wait for a brighter day to take the macros.
Pentax *ist DS, Pentax Spotmatic 35mm circa 1968
SMC-DA 18-55mm kit, SMC-F 70-200, S-M-C- TAKUMAR 35/2, S-M-C-Macro Takumar 50mm F/4, SMC Takumar 50/1.4, SMC-M 135/3.5, Super Takumar 300mm F/4
Pentax AF160T Flash
Amvona AT8588L Ball-Head tripod