Golems of unusual size

So I've been looking to make two new golems, or actually change the size of two golems. But I've hit a snag. While the DMG does give some details on INCREASING size, I can't seem to find anything on reducing size.

So.

How would one go about making a medium-sized iron golem and a huge-sized stone golem?

The iron golem would have been used for mining by dwarves (ownership being transferred like a shield guardian). So a weapon change would also be in place, from a (long?)sword to a (war)pick.

The stone golem would have been a defense mechanism, as they are two statues at the entrance to the dwarven stronghold, which can be awakened in time of need.

Besides hit dice, what would I need to change? Their base stats? ​

any tips??