I've also seen quite a few with shorter tube and judging by the colour scheme on yours, if 2cm is taken of no one will ever know, unless sold on here :)
But if it is done I would be careful with that hacksaw, certainly not a hand tool jobby, would get it cut by a pro, nice and clean
Not on this one I think steel is a bit thin on the top. And value would plummeted. Alu frames on the other hand have been done plenty of times, I have one at LBS right now to be done as the frame cost less than a seat post.
I've also seen quite a few with shorter tube and judging by the colour scheme on yours, if 2cm is taken of no one will ever know, unless sold on here :)
But if it is done I would be careful with that hacksaw, certainly not a hand tool jobby, would get it cut by a pro, nice and clean