mijostyn:
Thinking about it more it might be better to centrally locate the glass plates in a box with cardboard spacers (cardboard box with a top) and then wrap the box with the heating blanket.
This way the heat would be more evenly distributed.
I assume that many here may have digital thermometers with long wire leads for oven/grill cooking which could be used to monitor temp.
As already mentioned, lower temperature and additional time would seem to be the way to go, especially with DIY methods.
When I tried the glass oven method the oven used would maintain heat @ around 135-140 degrees (not any lower).
Doing so made the edge warp worse on a Pearl issue the "The Last Castrato".
I purchased another copy on line and it has a similar edge warp.
I only wanted to listen to it out of curiosity, so left it @ that (could not listen to the first cut on either side, and on the baked LP the first 2 cuts).
DeKay