Front was a ball ache though. I'm assuming the OP has Roadhog forks on their Roadrat already. The mudguard eyelets are in the 'normal' position. Fitting the calliper was a faff. need to turn the mount upside down and shim th ecalliper in and out to get the alignment right. Also turn the rotor round so it rotates in the right direction and then flip the hub. If your tyres are directional you need to swap it round too.
Regarding the Roadhog fork, with my last discs I fitted the mount upside down like you say, but the pads ended up not properly contacting the rotor resulting in a lip worn in them at the top, which caused rubbing after a while. I also didn't realise I'd worn the pads almost completely out as they looked fine through the viewing hole
When I fitted the BB5s I didn't want this to happen again (the pads really should contact the rotor correctly) so I fitted the mount the right way up. I just had to spend a couple of minutes with the file to remove a tiny bit of material from the top corner of it so it didn't foul the fork leg. It's very soft alloy and it's the tiniest bit of material that needs to go.
Now everything aligns properly