While hardwiring my dash cam today I realised that if I did not put the top spade of the fuse holder to the power side of the fusebox I would be bi-passing the actual fuse I was using for the camera, this meant turning the piggyback fuse upside down as the power side on my fuse starts at the bottom, done quite a few of these over the years and never gave it a thought. Am I right or am I missing something?

Don't really understand what you are saying without a picture.

A piggyback fuse holder normally has two fuse holders. One for the original and one for the dashcam fuse.

When I installed a dashcam, you remove the existing fuse from the fusebox slot that you will be using for the camera.
The original fuse and the dashcam fuse then fit into the piggyback fuse holder.

It is not bypassed. When you put a piggyback fuse in in the wrong way the current to the new device flows through both fuses. The only risk you have is that the combined current is too much for the original fuse.

Thank you Grumsel, so it is still better to put the top spade of the piggyback to the + side of the fuse insert then.

It's better to put them in the correct way. But it's no drama if you put them in the wrong way.

Click image to enlarge

Spot on grumble, I get it now, thank you very much for clarifying that for me.