So my folks have an Accord with the 1-piece plastic trunk tray. Thinking one would be nice for my '05 HCH, I went looking online. What I found, tho, were warnings noting that the regular Civic trunk tray can't be used in the hybrid model. Why? I thought it'd be ok, as the IMA cooling fan is at the top of the rear shelf, in the cabin. Does anyone know exactly why they can't be used in the HCH 1? As I'm kinda handy with plastics, I considered that it could be modified where it meets the seat back.

I don't have a HCH so I could be entirely wrong with this answer.

I have a trunk tray in my 07 HAH. Part listing for regular 07 Accord tray says not for use in a HAH. Reason, because it won't fit. The non hybrid Accord has a deeper trunk. The hybrid is missing about 4-6 inches or so up by the back seat. So they make a smaller tray.

I believe the same is true for the HCH. They do have a tray for the 06-09 HCH. 05??

Cheers

I asked regarding trunk tray for our HCHII when we purchased, and it wasn't available as yet. Likely for the same reasons: different trunk floor dimensions compared to regular civic, and less available due to small production run of the hybrid. I ended up just chucking a nice blanket in there, does the trick, except for really wet spills. We got the "all weather" floor mats (heavy duty black rubber, leave them in year 'round), which were pretty pricey, but worth it with our light interior color. I believe the trunk tray is similarly pricey. Seems to me it's less needed than the floormats.

I figured that out after staring at the trunk for a while, having forgotten the battery pack is there. But I found a solution.
Wal-Mart has a pretty nice bunch of various floor mats. Next to them, in a vertical stand, is replacement trunk carpeting. Since I already have that, I opted for the roll of vinyl named "Cargo/Utility Protection" made by Remington Ind. It's 47x32 and is almost wide enough to fit. I bought it for $15 and laid my carpet mat on top of it and trimmed it. It works pretty nice. The only downside is it only comes in grey or clear, no black.
I had gone to several fabric stores looking for the vinyl, but they wanted too much for it, and it didn't even have a pattern.
Note: if you do buy this mat, be warned...the pattern has different guide curve marks on the left and right side, which you may not notice before cutting. When I finished, I stared at it, thinking I had cut it wrong.