[Foobar]

Yes, my concern would only be underdosing.

[Bionic]

Well until Galileo came along you could drop one from a tower and time how long it took to fall  .
Mind you this method did have some drawbacks - one of which was that long wools produced inaccurate results due to the increased air resistance.

And of course the problem with this is that I don't have a tower 

[Dans]

I did ask at work for you Sally. Apparently scientists are as confounded as to how to do it. Holding the sheep on scales was the first vote with a piece of board resting on two scales being second. That or the hammock and spring balance as SitN suggested.

Underdosing a significant concern, but when it comes to fluking you also have to worry about overdosing when using flukiver or anything containing closantel.

Dans

[Bionic]

Thanks Dans,
I don't know yet what drench I will be giving them. The vet said they are able to give out small doses rather than me having to buy a whole bottle. It just depends on what they have open when I go in next week, but I will take into account what you have said if it contains closantel.
I am reasonably happy with the calculations I have but we are considering getting a spring balance. I can't believe how cheap they are. OH says he would be able to rig up a pulley and I guess I could use an old sheet for the sling.
 

[Dans]

There's a great table on this page outlining which drugs kill which age flukes.

http://www.scops.org.uk/endoparasites-liver-fluke.html

At this time of year you are often safe with one that kills adults but I did see a liver with some very small fluke in it today.

Dans

[DartmoorLiz]

I've recently bought a weigh crate off e-bay and I've found that its great for containing the more bouncy sheep which will jump out of the race as they can't jump out of the scales.  Of course, if you've only got eight then the chances are they're quiet and tame and nice to handle but its a potential vote in favour of scales.  I think I paid £200 but the worst was waiting for a set to come up in the area.  I know the chap I bought them from bought them from a farm auction so that's another place where you may pick some up cheap.

Before the scales we used a spring balance with the poor sheep in a builder's dumpy bag - which sounds awful but the sheep, once feet up in the hammock wern't that bothered.

[Bionic]

My spring balance just arrived this morning    Now all I have to do is to get OH to rig up some kind of pulley. Best talk nicely to him me thinks