ATM 8" mirror questions - weight, good sources, mirror cells?

[Matt Hughes <mhughes@qualcomm.com>]

Hi! I'm trying to build an 8-inch Dobsonian truss-tube scope. I know this
sounds a bit silly, but in large part I am doing it as an exercise
(cheaper, and good practice, and I can get it done faster) towards
building something around a 15" scope. Towards that end, I have read
Richard Berry's book, then Tectron's The Modern Dobsonian and AstroSystems
book on truss-tube dobs. I have a few questions:

1) How much is a "standard" 8-inch mirror going to weigh? I am trying to
calculate balance points, etc and am having problems because all weight
info in the AstroSystems book are for 12.5" and up scopes. 

2) I'm considering an approximately f/7 primary - what do people think of
this in terms of both optical quality and mechanical considerations? Seems
to me that that would allow a fairly reasonable tube length (and hopefully
somewhat reasonable mirror price as well).

3) What is a good place to get a nice 8-inch mirror? I've heard enough
nice things about Galaxy that I just called them - and was told they are
only doing 18" and up mirrors these days. They referred me to Jerry
Wilkinson at Wavefront Consulting - has anybody gotten a mirror from him?
How are they? What are delivery times like (I am fairly flexible, but it
would be nice to get the thing within 6 months or so, anyway)? Does
anybody have other recommendations (I'm leaning towards a more expensive,
higher quality mirror)?

4) The Tectron pamphlet really stressed the importance of a good mirror
cell. Is this still a significant thing down in the 8" range, or is
Berry's silicon-and-wood mount just as good? Who sells decent 8" 9-point
flotation cells? 

Thanks very much for any information!
                                                        Matt Hughes