There has not been any issue with T-Rex mod. Community mates are very happy with it =)
But the sp-mod #2 is faster and use less power on the 1080ti. 34MHASH @80% .
The T-rex miner needs 100% power and max 32MHASH. The t-rex miner is not free because it has a buildt in fee.
Sp_ mod is 0.05 BTC + an extra 2% dev fee. It does not make any sense. But mate, you are welcome to sell it. We are just suggesting what we think is fair. =)