Thanks for the reply.
Im not sure I understand 100%.. so let me try to regurgitate it back to you and see what Im missing here.. 
1.) because I successfully flashed Optiboot (using the Otiloader sketch.. that auto detects chip signature) in a jig/circuit that was set-up with 16MHz external crystal,..... I can just take that chip out.. and pop it into the 'final' circuit that is set-up to use an 8MHz external resonator.. and have ZERO problems? side effects?......nothing??
2.) There is no 'pre-existing' entry in the boards menu in the Arduino IDE for ANYTHING Optiboot related? 16Mhz or 8Mhz??
(kinda lost on that one I guess?)
I think there is actually 2 piece of info there that are useful (even if not usable currently) from the rest of you post:
A.)
There is no pre-existing definition in the Arduino IDE for a board with Optiboot at 8MHz, but it's easy to add one: Find the boards.txt file and duplicate the uno definition (the first block of text). Change the uno prefix in the duplicated text to something else, change upload.speed to 57600, change f_cpu to 8000000L, and change name to something else.
I would do/follow the above process if:
i.) I had an 8Mhz set-up (including crystal/resonator).. and wanted to flash Optiboot bootloader to a blank chip that is intended to run @ +3.3v & 8Mhz clock....yes?
(because Optiboot doesnt by default have a 8Mhz entry to use/burn)... correct?
B.)
Likewise you can burn a bootloader binary made for an 8MHz board onto a chip running at 16MHz. To test it with the 16MHz crystal you just need to upload at twice the normal baud, and to do that you make a new entry in boards.txt as described above.
now this seems like an answer to addresses my current situation/problem...(correct?)
I would do/follow the above process if: (like my current situation)
i.) I have a 16Mhz set-up for FLASHING the BOOTLOADER to the chip.. but in the end the FINAL circuit the chip will go into is a 8Mhz set-up?
So if I was to follow the above..
I would be making 2 NEW bootloader entries:
1.) 8Mhz >> 8Mhz Optiboot
and a
2.) 16Mhz >> 8Mhz Optiboot
entry.......yes?
and in theory.. (taking this another step)..
if my flashing/bootloader 'jig' was ONLY set-up as a 8Mhz set-up.... but the target chip was eventually going to go into a 16Mhz set-up..
I could make another (3rd) entry..
3.) 8Mhz >> 16Mhz Optiboot..
(or can you NOT be compatible that way? 8Mhz to 16Mhz?)
am I following you correctly so far?
And all this is done by duplicating the UNO (Optiboot) entry and renaming, and changing the upload rate?
and again.. no side-effects/problems flashing in one environment and using in another?
so giving it a try:.
here are my two new BOARDS.txt entries..
1 x straight 8Mhz (flashed in 8MHz circuit and used in final 8MHz circuit)
1 x 16Mhz to 8Mhz (flashed in 16MHz circuit and used in final 8MHz circuit)
optiboot_8MHz.name=Optiboot @ 8MHz
optiboot_8MHz.upload.protocol=arduino
optiboot_8MHz.upload.maximum_size=32256
optiboot_8MHz.upload.speed=57600
optiboot_8MHz.bootloader.low_fuses=0xff
optiboot_8MHz.bootloader.high_fuses=0xde
optiboot_8MHz.bootloader.extended_fuses=0x05
optiboot_8MHz.bootloader.path=optiboot
optiboot_8MHz.bootloader.file=optiboot_atmega328.hex
optiboot_8MHz.bootloader.unlock_bits=0x3F
optiboot_8MHz.bootloader.lock_bits=0x0F
optiboot_8MHz.build.mcu=atmega328p
optiboot_8MHz.build.f_cpu=8000000L
optiboot_8MHz.build.core=arduino
optiboot_8MHz.build.variant=standardoptiboot_16-8MHz.name=Optiboot 16MHz >> 8MHz
optiboot_16-8MHz.upload.protocol=arduino
optiboot_16-8MHz.upload.maximum_size=32256
optiboot_16-8MHz.upload.speed=115200
optiboot_16-8MHz.bootloader.low_fuses=0xff
optiboot_16-8MHz.bootloader.high_fuses=0xde
optiboot_16-8MHz.bootloader.extended_fuses=0x05
optiboot_16-8MHz.bootloader.path=optiboot
optiboot_16-8MHz.bootloader.file=optiboot_atmega328.hex
optiboot_16-8MHz.bootloader.unlock_bits=0x3F
optiboot_16-8MHz.bootloader.lock_bits=0x0F
optiboot_16-8MHz.build.mcu=atmega328p
optiboot_16-8MHz.build.f_cpu=8000000L
optiboot_16-8MHz.build.core=arduino
optiboot_16-8MHz.build.variant=standard
thanks!
thanks for reply too!