A few tyre queries - tubed/tubeless

[Buyasta]

I need to replace the tyres on my Scorpio, so that I can sit my restricted test.
I already bought a replacement set of tyres for it, as my brother had assured me they would be fine, and he is a great deal more knowledgeable about mechanical matters than me, but after a little more research, I'm now unsure whether or not I can actually use them, so I need a little advice.

The bike currently has the stock tyres on it, both tubed, an 80/100-18 front, and a 100/90-18 rear, on spoked wheels.
The replacement tyres I got are a 90/90-18 tubed front, and a 100/90-18 tubeless rear... These ones: http://www.cycletreads.co.nz/product...oad_tyres.aspx

Based on the fact that they are the only two tyres from that manufacturer that Cycletreads stock, it seems like they're intended to be used together, and it'd be ok to run them together, but in searching for information on mixing and matching tyre types, it has all related to different constructions, and I haven't found anything saying whether or not it is safe to run a mix of tubed and tubeless tyres.

I've also found much information saying that you can run tubeless tyres on spoked rims by just putting an inner tube in them, and that it is also possible to seal spoked wheels so you can run them tubeless.

As far as the slight change in size on the front goes, I know that they'll end up having pretty much the same profile, as 100% of 80 is 80 and 90% of 90 is 81, so they'll end up within a millimetre of each other, I'm just not sure how much leeway there is changing the width of tyres without changing the rims.

So my questions are as follows:
1. Is it safe to run a tubed front and tubeless rear?
2. Are there any disadvantages I need to be aware of in running a rear tubeless tyre with a tube in it?
3. Does anyone know how much it costs to get spoked rims sealed so you can run tubeless tyres on them?
4. Is going from an 80/100 to a 90/90 on the front going to be an issue, given the rim is designed for an 80/100?
5. Given the situation as laid out above, what is your advice - should I just get these tyres fitted, or get the manufacturers recommended tyres instead?

Thanks in advance for any answers and advice.

[RideLife]

I'm no expert.... But have been around bikes for years, and never heard of any disadvantage in running a TT and a TL together over two TT.
The 90/90 should be fine on the front. It may cause the steering to slow a little, but no big deal.

[Transalper]

I think you'll just mount both those tyres you've bought with tubes in and all will be fine.
Don't waist time and cash trying to seal up the spoked rim just to run a tubless tyre, in this case I'd just run it with a tube.

It (the scorpio) is not a high performance or big heavy beast so I can't see any issues but if you want an expert opinion go see Don at Pitlane.

[boman]

You can run a tube in a tubeless tyre. The only difference in the construction of the two, is the tubeless tyre has a membrane moulded into the inside of the tyre, so that it holds air, when mounted on a tubeless rim. On 99% of spoked wheels, a tube is necessary.