Mick,
Your Panther looks so good. That's a nice, clean build. The homely little China girl has a hot looking big sister I never knew about, it seems.
Regarding the 70mm drum brake. What kind is it? Much as I like the looks of drum brakes (I use them, too), my experience with them is disappointing in their stopping power. If yours is new it may well improve with kind of "seating in" through use, but don't expect a lot from it. I've experience with three makes in that size. This is my experience and maybe somebody else would rate the three differently. I've had a couple of the worksman and neither is much good. The wheels are good and the brake might be OK for a pedal bike, but not for what we're doing. The Sturmey Archer is noticeably better, but is still nothing to write home about. I understand that the bigger Sturmey Archer (90mm) is pretty good, but don't have personal experience so can't say how much better. I have also cleaned up old Atom hubs made in France and in 70mm they are better than the Worksman or the Sturmey Archer. Still not enough though if you've got some weight to stop at speed.
People swear by disc brakes and they are no doubt superior. Your bike would still look good using disc. Just last night I finished lacing up a replacement wheel for my heavy Panther with the sidecar. The new 11 gauge spokes came yesterday from HUsky bicycles. 9.5" long and fifty of them for $19.00 before shipping. The hub has been salvaged from an old Honda 55 trail bike and is beefy, 6" in diameter and looks to be very well made. I hope it works half way as good as it looks. I'll post a photo of the wheel when I have one. So, it may be that you will need to change out that wheel and use it on something else. Take a look around at light motorcycle hubs. Maybe something from a 125CC that was meant for racing. Even ones that look scuzzy will clean up nicely and look like new again. Or go disc. That's all I can suggest.
Nice job on the bike, mate.
SB