Hey nymickey;
From your description, the Weider 130 Slant Board does not convert to a Flat Bench position. I personally have three benches (matter of convenience, bought them over a period of time) but I do find the flat bench necessary for working the overall chest.
The incline/decline also works the chest but mainly the Upper/Lower portions. If you consider the W130SB try performing Dips (in place of the flat bench) which may help the overall chest plus the triceps. Just my 2 cents.