I use Kort's SC, which displays the imbue points from each gem. I'm not sure what formula determines the imbus value for various gems, but I do know that which ever gems has the highest value gets that value doubled before adding to the other gems' imbue values.
I just look at the point values from Kort's to see the numbers.
With crafted 5th slot gear there is another 'gem' present as far as imbue points go, so it will need to be added to that value (Kort's doesn't have a true 5th slot place holder, so I just write down the value on scratch paper). If you make a piece of dragonsworn or enhanced gear, delve it and see what its current bonus level is. That usually does a good job of telling you what the base imbue hidden value is. All you need to do usually is take 1/2 that number (provided you have another gem that has more imbue points than the inherent value on the naked piece.)
Hope I'm not confusing you too much, been up for 30 hours now, getting a little slap happy at this point.
Now with legendary weapons, the formula is a bit different, and you need to remember that you only get to add 3 gems to the item. I've had to rework a couple templates when the bonus level turned out to be 40-42 as a result.
Hopefully the template gods will answer with more definitive information!
-----signature-----
/dismiss ToA /hug Ventrilo
Friend of Kenda and Barlimann, I miss you both so much!
This game is my heroin.