New Tank Set-Up

Well, this is going to be the big weekend.  I plan to tear down my
tank, remove the undergravel plate, dip my Echinodorus and Java
Fern in potassium permanganate solution to get rid of the snail eggs,
and get set up for some serious aquascaping.

Based upon the collective wisdom I have gleaned from the List over
the past several months I have decided to start with a layer of peat
plates, then a fine gravel/laterite/Dupla root tablet layer, then an
additional layer of fine gravel (about double the thickness of the
gravel/laterite mix).  Finally, I  plan to add a fairly thin layer of
coarser gravel which can be vacuumed during water changes.  Any
comments about using the peat plates under the gravel?  My
motivation for using them is that I have read that crypts, and
perhaps other plants, will do better with some organic matter in the
substrate.  Does this seem like too much gravel for such a relatively
small tank (20 gal. Long, which has the same footprint as a 29gal.
but is only 12 3/4 inches high)?  My fish load is, I think, moderate (5
serpae tetras and 2 black mollies, and I plan to add an SAE).

I am using DIY CO2 following the sublimely simple design described
by Trent Honea, who, by the way, should get the Gatorade Award for
1996, and I have VHO lighting wired through my double bright strip
reflector, although I am currently running only 1 VHO Aquasun and 1
normal output full spectrum tube (both 24 in.)

A couple of questions remain:

Concerning the substrate... I have Tetra Hilena Crypto tablets.
Should these be added to the gravel/laterite/Dupla tablet mix, or is
this overkill?  Should they be used at all?

Concerning the lighting....Has anyone studied how much light is
attenuated by the plexiglass or plastic (or even glass for that matter)
shield that comes as part of our standard aquarium hoods?  When
we buy them they are nice and transparent, but generally get pretty
crudded up in a matter of months.  I know that on reef tanks, and
probably many planted ones, the DIY set-ups I have seen simply use
waterproof endcaps and bulb clips; and dispense entirely with the
glass and the canopy.  While this is probably more efficient, many of
these rigs look very unattractive.   I would like to hear some
comments on light attenuation from our lighting experts.

And finally... I am considering ordering driftwood and plants from
Aquarium Driftwood in Semmes, Alabama (1-800-600-4132).  They
have a homepage at www.pair.com/aqwood/index.htm.  Has anyone
out there had any experience with them?

I will also accept any advice proffered on what plants would work
well in such a small tank.  As already indicated, lighting should not
be a limiting factor.