A long-distance support situation involving a friend. ouch!!!!! OMG!!!!
It is not necessary or needful for computer builders to update from L9, since it has wonderful performance.
Updating is fast and easy. Safe mode is recommended. Testing is recommended after updating. If you get bad performance, just flash it again and re-test. You can see why computer builders would not care to go through this process. When building a computer, it is most necessary to provide a good software/hardware solution, and to provide a full restore-disc set. Then it becomes unnecessary to support user modifications because the system worked perfectly "as shipped".
In my experience, customers and family members will hold you to the maximum amount of support possible. After all, it's free for them: "Oh, you've just GOT to help me. After all, you built this !?&^ thing!" If you're building or repairing computers, support problems can bankrupt or even affect your health, so do follow industry standard practices to protect yourself. Make an additional system restore set on CD for your files as this is the number one defense against the user modification support liability. If possible, strongly insist that there is no support if the unit has been used without the protection of a battery backup unit (UPS). Support only the software included with the unit and on the restore discs (that you have made; see Norton Ghost). That way, you don't have to worry about user modifications or viruses invalidating your product.
From a support standpoint for the BenQ, firmwares L9 and P9 are ideal because they are the least trouble. Changing the firmware means that you need to test and document that the unit performs well after modification. Not changing the firmware means that it's up to BenQ. Above all, test, document, and preserve that the computer system performs well "as shipped" in fully valid condition.
Oh, and either marry the friend or get a phone plan with unlimited long-distance.
I wouldn't wish that support situation on anybody. If the friend or family member doesn't live in the same house, play dumb, get absent fast, anything to avoid their computer. . .oh, there are no words to describe the trouble. Speechless! I'm speechless!! It's a first.