neur0n has released updates for both of his custom firmwares! Both 6.37 ME v7 and 6.35 Beta v18!
Like the others in the past, 6.35 is for PSP 2000 models only, but its update brings some cool improvements:
• Adding PluginManager to the VshMenu
• Removal of “Execute BOOT.BIN” option from RecoveryMenu
• Update of the NidResolver
• And supports custom PS1 DOCUMENT.DAT files
Of course, v7 of 6.37 ME has the same updates of:
• Adding PluginManager to the VshMenu
• Removal of “Execute BOOT.BIN” option from RecoveryMenu
• Update of the NidResolver
• And supports custom PS1 DOCUMENT.DAT files

To install the 6.37 ME v7 custom firmware, first, you need to install CFW or HEN like 5.00M33 or 6.35PRO onto your PSP, and then:

• Copy UPDATE folder at ms0:/PSP/GAME/.
• Put 6.37 official update at ms0:/PSP/GAME/UPDATE/637.PBP .
• Run installer from xmb.

What is probably the best feature on this is that if you hold the Right trigger whenever you turn your PSP on, it turns it to the recovery menu like most custom firmwares. But when you hold the Home button, you can boot official firmware!

Discussion: Here
Source 1: Here
Source 2: Here
Download 1: Here
Download 2: Here