Brother, I wouldn't use any W&B computing assistance until I could "walk and chew gum at the same time" weight and balance-wise. Buy a calculator and a scratch pad, until you can. "GIGO" in a critical W&B computation will make you a sudden test pilot, and it's killed lottsa guys- you may not know you have an issue until you're deeply involved trying to survive it.
On the top of the scratch pad, put your aircraft's WT, MOM, and ARM (CG). Note the half dozen or so stations from the RFM. I'd shoot a copy of the fuel CG if it's irregular, like the 206 is, and do all this on the back of it. As you figure the actual, write'm down. Adjust with each change, for instance after a landing without cargo or passenger cahnge, all you gotta do is calculate the fuel burn's effect. A 2-memory calculator and some practice, you can do this quicker than you can write the result- I know, I've done this a hundred or so times in a day, many times.
If you're dead set on fiddling with more than this, issues arise:
How are you going to accurately place the weight? Is it reliably weighed, with it's CG marked?
How are you going to secure it at the designated station? This is why many loads are palletized.
How do you place it- are there indexes on your aircraft you can measure from?
Can you compute the lateral CG of the proposed load?
And the vertical?
Once you have a good understanding of all this, you'll have a chance of recognizing a calculated error, no matter how it arises.
It's really a bad feeling to run out of control authority. You don't want to do it casually.