I’ve received the Sofirn C8F 21700 version that I ordered from Sofirn’s AliExpress store, so I’ll write only based on my experience.
1) There doesn’t seem to be a discount code, however, there may sometimes be multiple (2 or 3) product links for some of the more popular Sofirn products, and sometimes, one listing might be slightly cheaper than the other listing. Be sure to check they are the same item (as of last checking, the C8F 21700 has only 1 listing, but other Sofirn lights usually have at least 2 listings… just my observation)
If you’ve been purchasing from AliExpress for some time, you may notice they have 3 types of discounts (and they can be cumulative):
a) AliExpress Select coupons = you are entitled to use the Select coupon to get a discount when you purchase over a certain amount
(how to get AliExpress Select coupons - use your ‘coins’ to exchange them, and also some other ‘activities’ on the phone app allows you to get that)
(you need to have the Select coupon first, before you can apply the discount)
b) store discount = this is a straight discount of a certain xx amount when you purchase yy amount (it’s automatic, you don’t have to do anything)
c) seller discount = you just grab this coupon from the store, they are free to get (but have a limit, eg. you can get this type of coupon once every how many days or weeks), it’s applied in the same way as the Select coupon (xx discount when you purchase yy amount)
by judiciously using the above methods, you can achieve your desired discounts (well, the key is for you to “spend” more money to get more discounts…)
2) Most Sofirn lights seem to list 5350-5750K as their tint, and I’ve sometimes ordered same Sofirn light but they appear slightly different tint, but likely within the 5350-5750K. As I don’t have something to check color temperature, I notice that the earlier Sofirn C8F (I got before) compared to the Sofirn C8F 21700 (which I just got) = in my specific samples, both of them seem to be somewhat in the cool neutral-white, but my Sofirn C8F seems to have a very slightly ‘rosier’ tint than the one on the C8F 21700. I believe this is just due to sample differences and another C8F 21700 might possibly also have the “slightly rosier’ tint too.
3) I think a cell with at least 10 amps or more continuous discharge current would be best. I did include the Sofirn 21700 since such batteries are very hard to find and expensive in our country (and most foreign online stores do not ship batteries to my country; so I now have to buy batteries with flashlights if possible). I used MC3000 to test capacity of the Sofirn 4000mAh 21700 and it got a bit over 4000mAh (drain to 2.75v cut-off). Since I don’t have another 21700 at the moment, I can’t say if it’s better or worse, but it appears to be a good battery — it’s flat-top and unprotected. The IR measurement from the MC3000 for the Sofirn 4000mAh 21700 is around 25mOhms (adjusting the battery in my MC3000 can slightly affect the IR reading).
4) issues? Well, I think someone above also has both the previous C8F (18650) and the C8F 21700. In my unscientific observation / testing, it seems that my C8F (18650) is slightly brighter on Turbo than the C8F 21700 on Turbo mode. Using a clamp meter, I’ve measured 10+ amps tailcap current reading on the C8F 18650 before, but on the C8F 21700, I’m getting around 7.8 amps only (I checked that the spring-bypass wires are still intact on that unit).
(note: the spring-bypass wire on my C8F 18650 seems to have just broke off, now the tailcap reading is around 7.8 amps too. As of now, I don’t have a soldering iron and the skill needed to reconnect the spring-bypass wire of my C8F 18650…).
I think ramping speed has been mentioned… it seems to work similarly as the ramping on the SP32A v2.0 — it may not be as smooth as NarsilM, but seems to be pretty good (probably around 4 seconds from min to max).