Draw contour data on slice with a patch

I'm having trouble making a contour of my volume data on a plane with specified coordinates designed for patch.

I have 5 slices I am looking to make along the span of a wing.

% set of plane coordinates for wing
xp = [0.2415 -4.0886 -4.5716 -0.2415];
yp = [0.1294 0.1294 -0.1294 -0.1294];
zp = [-0.4183 -2.9183 -2.0817 0.4183];

figure
patch(xp,yp,zp,'g') % draw wing
hold on

% I guess if you want to try running this replace Xw Yw Zw with -4:0.2:4 and Slice_var with flow or something

for i=1:length(spx1)    
   h = slice(Xw,Yw,Zw,Slice_var,...
       [spx1(i) spx1(i) spx2(i) spx2(i)],...
       [yp(4) yp(1)+1 yp(1)+1 yp(4)],...
       [spz1(i) spz1(i) spz2(i) spz2(i)]);

   set(h,'edgecolor','none')
end

figure
patch(xp,yp,zp,'g') % draw wing
hold on

% slice planes
spx1 = xp(1):(xp(2)-xp(1))/5:xp(2); spx2 = xp(4):(xp(3)-xp(4))/5:xp(3);
spz1 = zp(1):(zp(2)-zp(1))/5:zp(2); spz2 = zp(4):(zp(3)-zp(4))/5:zp(3);

for i=1:length(spx1)
    patch([spx1(i) spx1(i) spx2(i) spx2(i)],...
         [yp(4) yp(1)+1 yp(1)+1 yp(4)],...
         [spz1(i) spz1(i) spz2(i) spz2(i)],'b');
end

When I try to make my contour plots, instead of making 5 slices along the span I get slices in the xy, yz, and xz planes. I would like to have my contours on these blue slices in the second image.