I installed an 8" Beckson deck plate in my Scamp
tank for easy access and used 5200 as well. I don't think the tank's strength has been compromised much if at all. Got it from Amazon. Has a clear lid, though other colors are available and slightly less expensive.
Beckson Deck Plate Installation Instructions
4" , 6" and 8" Deck Plate Installation Instructions
1. Remove deck plate center, invert, and use as a template to scribe cut line.
Go to Step 2
5" Deck Plate Installation Instructions
1. Remove deck plate center. Using the deck plate outer ring as the template and scribe line around the inside of the ring.
2. Drill 3/8" (9.2mm) starter hole adjacent to inside scribed line. Cut 1/8" (3.2mm) outside of the line (larger) with a reciprocal saw.
3. When using self-tapping screws on a deck of sufficient thickness, mount deck plate and drill screw holes partially into the deck with 1/8" (3.2mm) drill bit.. When thru- bolting, drill all the way through the deck.
Deck construction (Solid Fiberglass, or Foam or Wood core)
4. For solid fiberglass decks proceed to step 5. On a foam or balsa core deck dig out 1/8" (3.2mm) of core bordering the primary hole and around the screw holes. Fill with two-part epoxy filler and let cure. Re-drill screw holes.
5. Replace center into the deck plate ring and apply a 3/8" (9.2mm) bead of silicone caulk on the edge of the spigot (flange) and under side of ring.
Beckson recommends using only silicone sealants for ABS deck plate installations and is not liable for product damage caused by other sealants.
See Easy Clean-Up below.
Note: For installation of polypropylene deck plates, please consult your local marine dealer or caulk manufacturer for best results. Silicone will not adhere to polypropylene.
6. Fasten deck plate to deck with #8 pan head screws or thru-bolts, maintaining a minimum of 1/16" (1.6mm) of caulk as a gasket and keeping the plate flat. If on a curved surface, fill gaps completely with caulk, without bending the trim ring. Thin ring deck plates may be mounted without fasteners. If adhesion is questionable, drill and counter bore thin ring for #8 fasteners.
Do not use countersunk or oval head screws. Damage will result.
7. Note: For Easy Clean-Up when installing ABS deck plates with silicone sealant: dry mount the deck plate, and apply liquid soap to a damp sponge. Carefully wipe all areas where you do not want silicone to stick. Remove and install with a generous amount of silicone sealant. Do not squeeze out caulk beyond the edge of the ring. Carefully remove excess with a single edged razor blade or "Exacto" knife once cured.
Do not scrape the deck or the deck plate with the razor blade. If necessary, remove excess caulk with isopropyl alcohol and a soft cloth.
If necessary - lubricate deck plate thread with Teflon grease or Vaseline.