I agree 100% regarding preboot difficulty generally when using the 'screen hold' method, however it's often overlooked that most healthy [not 'bricked'] units can easily enter preboot by simply holding the battery symbol for 5 or 6 seconds to access the hidden menu which in fact performs a boot-block. The unit is therefore in preboot for all intents and purposes and will stay that way indefinitely, until the menu is exited or the unit powered off, thus allowing RGN flashing with Updater.exe to be done without any haste. I added that as a note to [Only registered and activated users can see links. ] a while back because i was surprised just how few ppl knew about it, including some reasonably experienced users even though you mentioned it prominently in the [Only registered and activated users can see links. ], and it's also mentioned other places in here too.
In a healthy unit, it's absolutely both bullet-proof and fool-proof to remove gupdate.gcd if present, enter preboot thru hidden menu and then flash upgrade or downgrade version as XXXX01000xxx.rgn with Updater.exe because it reduced chance of bricking to zero in my experience with hundreds of such flashings.