He Fwee,
Good to see you back and active on the boards.
Two schools of thought here.
1. I know a lot of people here who have used water bottles, 2 liter coke bottles, milk bottles etc. all plastic that have had great results and no problems with infection, off-flavors, etc. I have sampled several different meads that have gone through primary in this manner and have not been able to detect any flavor influence from the plastic container. I've also done blind-tastings plastic vs. glass vs. stainless and was unable to distinguish between the three, along with a panel of about four other meadmakers who all were not able call the plastic out. I say GFI (Go For It)
2. I've done the same taste test comparison with secondary aging in plastic water bottle jugs, PET bottles and glass. In this case three of the panel did pick out two of the plastic secondary vessels, and these were both the plastic water bottle jugs that are the typical kind that you find in a grocery store that are thin, opaque plastic and squarish with a handle and a colored snap on cap. Interestingly the one judge who swore up and down before the tasting that he would have no problem telling the difference called out one of the glass vessels as the plastic secondary.
Hope that helps,
Oskaar