Yep I'm using the EM3EV bags too (de-badged), same time as buying the kits. I got extra the 2nd time to use as frame bags for other non-electric bikes. It's so convenient, bike-packing has made frame bags popular for regular bikes in that way too, but those are much more expensive expedition bags. My pedal bikes still have room for a litre drink bottle on the seat tube for on-bike access, fully utilising the diamond frame.
On the Merida pictured I've got the 50V 25Ah pack in the EM3EV bag under tension to the head tube with 7.6mm wide 85MPa tensile cable ties outdoor UV rated all daisy chained as one loop, hidden within an old 23c bike tube to not rub the frame. Secondary 4.8mm wide ties of same spec use the cable guide tabs to stay the bag in all directions, the double frame top tube to seat tube is a bonus for this and locking up the bike as well.
The main strap to head tube doubled as a mount to to strap my Lezyne HV bike pump to, but now I've got solid Tannus 32c tyres with 29er wheels in the 26 inch frame as pictured, I don't even need tubes, patch kit or pump anymore. Like bike-packing I have a direct seat post mount rear pack using a Topeak handlebar quick release TourGuide handlebar pack mounted sideways, clears full suspension travel.
PS: only one size of EM3EV bag.
Recreational: BBSHD 100mm on fat bike through a Rohloff XL, soft programming gentle on the hub, pedal only and long range capable.
Civil duty: Corratec 29er Diamond Trekking Bosch Performance Line 400Wh Alfine 8sp, auxiliary battery port.
History: Front hub SS 200W, China E-mtb 200W, 3x A2B Metros, Commuter Booster beta, 2.4kW d/s w/DD kit, MAC 1.5kW road/flatbar 1250Wh EM3EV frame batt, BBS02 750W d/s MTB 1250Wh frame batt. All sold (except A2B Metros).