I already have level 5 access to Farseer. I want to know if an FSD has to mounted on a ship to be modded. I want to take my Asp (has a 5A FSD) down to see her. Then have 2 6A FSD's that I bought at KP Tauri transported down to Farseer. After she mods them I fly back to KP Tauri and have the modded 6A FSD's transported back to KP Tauri. Reason for this. My Asp has a 50+LY range so it's a quick trip and I have an Anaconda I'm outfitting for long range exploration at KP tauri.
i think it would work if you strip down the anaconda and fit in the 5A FSD which have the grade 5 mods. Take that and then the rest of your plan should work as you have to put them on a ship to engineer it
You can modify smaller size modules, as long as they can be fitted e.g. certain thrusters can't be fitted above a certain mass of ship. However, you can't fit size 6 into a size 5 slot / bay so that is your issue with the Asp - the 'conda would be OK for fitting and modding smaller modules though.