Long boy names cute Nn?

We are set on picking a long boy name that can be shortened to something - we have a selection of girl names if bump is female but stuck on the boy names!

I'm trying to find something that isnt too common (Thomas, Theodore, Tobias) or too out there!

Partner likes Reginald (Reggie), Lancelot (Lance)

I like Percival (Percy) and Alphonse (Alphie)

Last name begins with P so that may rule out Percival!

We did discuss Montgomery (Monty) but I'm not sure if we can pull that off...