When I resize clip I see red right border, such UI signal looks like nothing at the right and I cannot stretch. I suggest onhover of the border to be green when it is possible to stretch right and red when this is the end already.
You should know if the clip duration can be increased by comparing the current time position with the total duration of the clip you are using. It’s not rocket science.
When two clips are next to each other, you need to be able to clearly distinguish between A’s trim-out handle and B’s trim-in handle. Your change breaks that and offers no solution for it.