Is it "done" or under-done?

I've been using polymer clay for 12 years, maybe a little more. I
know that recently the makers of FIMO have lowered the recommended
bake temperature. Because I rent, I have always been at the mercy of
whatever oven landlords provided. Because of this, for a long time, I
used a small toaster oven (even though that is not recommended). For
the last couple of years I have been using a larger toaster oven
(outside dimensions 11 in. W by 11 in. deep by 16.5 in. high)
manufactured by GE and sold by Wal-Mart. I have made "creatures" in
the past that were fairly large, but I just winged it and hoped for
the best. I was setting the oven at 265.
..
I'm working on a multi-color heart for an injured veteran of the Iraq
war. I pirated small picture frames from key chains and plan to
suspend them at intervals from the heart so his family can put
favorite photos in them. The heart is open, like an outline; that
"outline" is about an inch wide by half an inch deep. The overall
heart shape is approximately 9 inches at its tallest point by 7 inches
at the widest point.
..
If memory serves I baked this about 40 minutes with the temperature
set at about 250 because an oven thermometer shows that this oven when
set at 250 cycles between about 220 degrees and 260 degrees. I was
inserting wire in holes I poked in the clay before I baked it. The
wire is what the frames will be suspended from. The clay around the
holes crumbled slightly, although I was working it roughly. I am
always hyper-concerned about stuff I make that goes out into the
world...whether it will hold up and is of good quality.
..
Because of this I am wondering if anyone else has input on baking
methods, times, etc. Most of the clay in this heart is FIMO, but
there is PRIMO in it, too. I'm concerned because the idea of the
heart is for it to hang...like on an I.V. pole. I've made hearts
before that have dangled from I.V. poles, swinging and bumping, and
there hasn't been a problem. However, those were perhaps 3 in. wide
by 4.5 in. tall and 1/4 to 1/2 in. thick.
..
I'm sorry this post is so long, especially for a first-time poster. I
became aware of this group when I read stuff on the web about the new
FIMO baking temperature.
Thanks!