I intend to have the trapdoor closed (it's the trapdoor sent with the 1240, so it has a hole for the fan to blow air through), so wouldn't that provide the pressure you describe?
People have said that a glue gun for this job is a bad idea, but haven't said why, apart from the point about applying pressure, which hopefully is addressed by the custom trapdoor (which doesn't expose the whole HSF, just the fan).
I think people's main concern is the initial thought that the glue is being used *between* the CPU and heatsink, which is would be worse than having no heatsink at all. The thing is, like I said, that the glue itself is soft and easily deformed once in place, moreso because the heatsink will get hot, and any movement off flat at all can be catastrophic for a hot processor. The 040, while hot, can probably tolerate a bit of abuse, but even so... I guess if the trapdoor applies enough pressure _evenly_ it should be fine, but you'd want to be sure it can't creep away from the CPU on one side, and that the board itself is flat and supported from behind.
I'm reminded of a time when I used to sell PC components over the counter in an electronics store. We had one guy return a motherboard/CPU combo for a refund, claiming it only worked for a few seconds. A quick examination found that he had put the heatsink on with a piece of self-adhesive foam padding, right over the heatsink contact surface on an Athlon XP chip... An excellent insulator! Needless to say he didn't get the refund as the CPU was working fine until he cooked it!
