Falling sand who should not despawn

As always, I try to find a way to break minecraft rule, and I find something interessant : I found a way to have a falling sand standing on the ground. This falling sand don't pop even beyond 600 ticks.

The easy little trick is to make the falling sand fall on block 36.

But I sometime notice that some of the falling sand disappear without any reason (very rare time), and it start being very annoying, because you can do many funny stuff with these falling blocks but sometime they sink in nowhere.

I also find why these block disappear : the fallTime variable of the falling entity is an Integer, but the "Time" tag is a byte. It means that sometimes, when the falling entity is saved, the fallTime is cast to byte and this value become wrong and this value become sometime 0 and when the fallTime = 0, the entity died.
I know that to fix that, you shouldn't just change the tag type from byte to integer, but please fix this, it will allow many funny things (like this : http://imgur.com/a/mYkkv).