Shouldn`t be hard at all. Hours are hours. Period. As previously mentioned, you can keep your hours under FAA regs in your FAA logbook, and begin your JAA logbook by writing "hours transferred from FAA logbook" at the beginning or the first page
. Don`t get hung up on thinking about what you think employers are thinking about, and think that you will be given the third degree about your hours, because you won`t
. They might want to know how you got your hours... "I flew as CFI in the US, before coming back to convert my licenses" covers those bases nicely
. The NCAA know (or at least they should by now) that license conversions from the FAA isn`t a big deal. Your examiner will not start adding up your hours with a calculator, and splitting them into IFR, simulated and/or actual... and so on