Stick on weights on the inside is fine. If your rims are good quality the only weight difference is the valve. Make sure they position the tyres on the rims correctly. The tyre should be marked with a white or yellow dot, this goes in line with the valve. I bet 99% of tyres are fitted incorrectly needing huge globs of lead.
http://www.toyo.com.au/tech_info14.htm
How many people have now just gone to the shed to check their tyres?
I can comment on the Vintage pin drive wheels and with the tyres fitted correctly only 1 or two thumbnail size leads were required on the back of each wheel.
Try the wheel on the wheel balancer without the tyre first to see how out of balance the bare wheel is.