Feel free to pay them the way you like it. I'm sure the possibility of a chargeback is some additional security, but I've used BTC to invest into it.
About the other problems: They may have some technical gliches but are very very friendly. Some arguments which convinced me:
- They offer to show you their ID-scans and personal data when you want this
- They showed details of their order of the KnCs
- Their whole story looks legit to me and they are currently offering to a small circle already some miners (ask them for a proof, if you are unsure)
- If they would scam, they wouldn't invest time/ressources into their website (which is ready for real use, what you can see when your account is activated)
- They have replied to me with real names sometimes
- They are not offshore, they live in Scandinavia and KnC is produced there too
- They offer a refund if KnC delivers not till the end of march
- They offer a general 14 days money back guarantee
- They take a 10% fee from the payouts which makes only sense if they payout
There isn't any 100% proof for nearly anything. But for me this is enough. As I said, I personaly think the worst what could happen with this guys would be if they have to refund because KnC doesn't deliver. Try to see it from their view too: What else could they do to proof that they are legit?
If the machines have more than 3 TH I doesn't care as long as I and people who found them via me get what we have on our contract. They are clearly defining the borders. If there are getting more than 3 TH, they could be perhaps extremly generous and reduce the 10% fee (you have to ask them).
Addtitionaly (again): Use this calc
http://btcinvest.net/en/bitcoin-mining-profit-calculator.php?diff=2193847870&dcosts=1200&diff_mincrease=30&blpbtc=25&dhsmhs=300000&diff_mincreasedecrease=3&btcusd=849.32&dpowcon=0&btcusd_mincrease=1&pcost=0&calcweeks=32&dleadtime=4&action=calc to calculate what it means when they have delays or ajust it according your predicitions and decide then.
This calculation is too positive.
You are saying that the difficulty increments will decrease each jump by 3%, this is so wrong...
As soon as all the Cointerra units start mining... haha, I think we will see jumps of 35% or higher.
You are also including that bitcoin will be worth 1% more with each jump, this is very speculative, could be 10% or maybe -10%.
AND you are forgetting the 10% fee...
AND your calculation starts from today...