ARC REF 5SE Cover Warping

I am considering purchase of a Ref 5SE, and one thing I've read about the preamp is that the acrylic cover can warp over time (presumably due to heat).

If you own this preamp, and you've noticed the same issue, what do you do about it? Leave the cover on and forget about it? Keep the cover off at all times?

ARC says that both their amps and preamps sound better with the top removed or with a acrylic cover. I just don't like the acrylic covers. I have the standard steel tops and just run both my amp and preamp without the tops. They run a little cooler with better air flow. When turned off I put black towels over them to keep the dust out. Though I am thinking of having custom covers made from a ham radio cover place to replace the towels.
Hi,theres a lot of heat coming off the power tube.They all would do it,i recon.There must be a reason they went that way.I wouldn't worry about it too much.
If it happens within the warranty period, send it back. If it doesn't warp in the first 3-years, you are probably okay.
The acrylic tops will warp. The key is to leave at least 8 inches clearance on the top of the amp. The problem is, people are jamming their amps into shelving with only a couple of inches clearance causing the heat to pool in the center of the acrylic cover.