Isn't 500ml of tyre sealant in each tyre going to make a hell of a negative difference in rotational weight?

Yes. But you don't need anywhere near 500ml.

100-125ml is more than enough IMHO.

500 ml? Who's suggesting you put that much in? I use 60ml of stans each end. I think I might actaully have used less than that for UST tyres.

oh!……….shit! Any tips on how to get some (well, lots) of it out without making the mother of all messes?
I wondered why my new wheels felt a bit (well, very) heavy 😳

Syringe

Well, I'm using Continental thin as tissue Speed Kings (non tubeless) and on the third and final go at getting them to stay up, I whacked a load in each and only when I was tidying up did I realise I'd just about emptied a big bottle.
Hahahaha! What a plank! I thought I was starting with some hideous illness when I could barely get up the road 😆

Ha Ha Ha!! 🙂

Deflate and pop the bead then use a syringe like uplink says.

Quality. 😆

I've just asked my wife if she can get me a syringe big enough to carry out this delicate procedure. She says she injects people not elephants :-).
Oh well, at least I've managed one giggle (all be it at myself) this wretched of weekends.
I sometimes wonder if I should be allowed out on my own. I don't know what goes on in my own head sometimes……..

I sometimes wonder if I should be aloud out on my own. I don't know what goes on in my own head sometimes……..

No, I'd keep things like this to myself! 😉

In all seriousness, if you've really put 500ml of sealant in I'd be looking at syphoning it out – or removing the tyre and starting again.

Stans do a syringe that screws onto the valve. You could then remove some sealant without breaking the bead. if you're near Nottingham, you can borrow mine.

Excellent! Stans are aware that there is at least one desperate numpty (me) bound to get a bit frustrated (or over excited) and whack a enough in for 5 tyres?
Thanks for the very kind offer Onzadog but I'm in Stockport.
I'll get to it tomorrow evening. I have a ride of ridiculous duration planned for Wednesday (it'll be my birthday) and for a reason that may be quite obvious, I'm looking forward to it with much more enthusiasm now than I was an hour ago.
Still, if you can't laugh at yourself and all that.