Question: How to show odeplot better?

I have a set of differential equations on 3 variables, B[1],B[2] and C. Its not physically meaningful for B[1]+B[2]>0.5 so i would ideally like to replace the cube that the solutions are displayed on (the axis take the limits B[1]=0...0.5,B[2]=0...0.5,C=0...100 ) with a triangular prism (the axis take the limits B[1]=0...0.5,B[2]=0...0.5,B[1]+B[2]<0.5,C=0...100 ).

Failing that i'd like the plot to display a plane showing where the meaningful values for the variables end.

here is the code I use to put the ODEplot together

Model := [diff(B[1](t), t) = k[a1]*C(t)*(R-B[1](t)-B[2](t))-k[d1]*B[1](t), diff(B[2](t), t) = k[a2]*C(t)*(R-B[1](t)-B[2](t))-k[d2]*B[2](t), diff(C(t), t) = (-(k[a1]+k[a2])*C(t)*(R-B[1](t)-B[2](t))+k[d1]*B[1](t)+k[d2]*B[2](t)+k[m]*((I)(t)-C(t)))/h];
DissMod := subs((I)(t) = 0, Model);
AssMod := subs((I)(t) = C[T], Model);

Pars1a := [k[a1] = 6*10^(-4), k[d1] = 7*10^(-3), k[a2] = 6*10^(-4), k[d2] = (7/5)*10^(-3), R = .5, k[m] = 10^(-4), C[T] = 100, h = 10^(-6)];

Pars := Pars1a; thing11 := subs(Pars, AssMod[1]), subs(Pars, AssMod[2]); thing12 := diff(C(t), t) = piecewise(t <= 100, subs(Pars, rhs(AssMod[3])), subs(Pars, rhs(DissMod[3]))); sol := dsolve({thing11, thing12, C(0) = 0, B[1](0) = 0, B[2](0) = 0}, {C(t), B[1](t), B[2](t)}, numeric, output = listprocedure, maxstep = 2, maxfun = 1000000); ParsPlot1a := odeplot(sol, [B[1](t), B[2](t), C(t)], t = 0 .. 700, color = blue, view = [0 .. .5, 0 .. .5, 0 .. 100], tickmarks = [[0 = 0, .5 = R], [0 = 0, .5 = R], [0 = 0, 25 = (1/4)*C[T], 50 = (1/2)*C[T], 100 = C[T]]]);


But I can't see a way of either making the plane or making the ODEplot axis into something other than a cube.