New Shiftstone: Sturdy Stone
Sturdy Stone works somewhat like Charge Stone in that it works as an extension of Hold. However, Sturdy Stone would only work on grounded held structures. When grounded and held for more than one second, a structure would enter the "sturdy" state, which would give the structure +1 to its weight, like when a structure is moving or grounded. The state initiates after one second, and lasts for one more second per second held after breaking the hold after it's already active up to some number of seconds (thinking 10 but that might be OP). To be clear:
0 seconds of hold - No effect
1 second of hold - Initiates for a single frame, basically no effect
1.5 seconds of hold - Initiates for half a second during the hold, and stops
2 seconds of hold - Initiates for a second during the hold and then persists for a second after
1 + max seconds - Initiates for max seconds during the hold and then persists for max seconds after
2 + max seconds - Initiates for 1 + max seconds during the hold and then persists for max seconds after
This sturdy state persists until either the object is regrounded (ungrounding does not affect it), the object is broken, or it naturally ends via the timer running out. Possibly, the sturdy state could escape the timer limit by the same way that the charged state is preserved (unholding the structure), although that might just be OP.
EDIT:
Possibly (?) the structure would be harder to destroy during the Sturdy Sate otherwise, making ricochets more likely and multi-structure or surface tension mounts easier to pull off at the expense of setup.