Hi, I have installed Optima red tops in both Jettas (00 and 01), no problems with installation. The 00 fit right in without mods, the 01 I have to cut a zip tie holding the positive cable and move it a little to reach. The batteries are only rated for 800 CCA but they have a HUGE reserve capacity. I had gelling fuel the other day and it cranked for a total of 4 minutes over 3 days and still started the car fine, my old 87 Jetta has 30 seconds tops of cranking on its new regular battery. I recently learned that Optima recommends a deep cycle battery for diesel applications though, (yellow top), I paid $230 CAD for mine no idea how much more the deep cycle is. I saw the red tops for $100 USD on many websites, a much better deal!
I will never buy a lead acid battery again after owning these Optima gel cells, they are truly a cut above (like switching to synthetic oil)
Greg