ATI Radeon HD4850 - safe voltage on air

As this is my first post on this forums - hi all.

I'm planning to buy Sapphire ATI Radeon HD4850 512MB Toxic with changed cooling solution - Zalman VF-900Cu and heatsinks on VRM and RAM. Maybe I add some 12cm fan near graphics card and more heatsinks to naked places if I have to. I think this is good cooling enough to do some pencil mod. Can I safely increase vGPU to 1,4V (24/7 work, not benchmark only) constantly controlling temperature of GPU and voltage of course? What do you think, does VRM hang on this? I can give max RPMs to fan, because noise doesn't bother me.

http://forums.techpowerup.com/showthread.php?t=64217

As we can see, there is really easy pencil mod if we want to increase voltage maximally to 1,4V. I understand that if I want to increase voltage to 1,4V, I can maximally pencil this first resistor without any consequences, because maximum voltage which I can achieve that way is 1,4V? Am I right?

But vGPU is not all. There is vRAM too. Is there any sense to do that mod too? Is OC of RAM on that VGA needed to see difference if we want to extremally OC GPU? Are heatsinks with air from fan enough to safely do that mod? If yes, what voltage of RAM is safe to 24/7 work?

Thanks in advance for the answers and sorry for my bad english.