Axis errors on rendering movie using trisurf

Hi there. I am trying to render frames of data, each frame of which is a trisurf. I have two subplots, each containing axis which I have manually set the xyz limits of. However, at some point in the movie, the trisurf exceeds the limits of one of the axis and rescales which looks awful. I have tried setting the axis limits to be larger but it doesn't make any difference. Can anyone suggest what might be wrong. I don't know what property I should be adjusting. Here is some of my code.

   subplot(1, 2, 1);
   axis([-60 120 -150 85 710 800]);
   a1 = gca;
   subplot(1, 2, 2);
   axis([-60 120 -150 85 710 800]);
   a2 = gca;

   for k = 1:size(obj.pts, 3)
   %add data to frame
   trisurf(obj.triangulation, vid1(1,:,k), vid1(2,:,k), vid1(3,:,k), 'Parent', a1, 'EdgeColor','none', 'FaceColor', [205 133 63] / 255);
   set(a1, 'CameraPosition', [30 -20 -116.025],...
   'CameraUpVector',[0 -1 0]);
   light('Parent', a1, 'Style', 'local');

   trisurf(obj.triangulation, vid2(1,:,k), vid2(2,:,k), vid2(3,:,k), 'Parent', a2, 'EdgeColor',    'none', 'FaceColor', [205 133 63] / 255);
   set(a2, 'CameraPosition', [30 -20 -116.025],...
   'CameraUpVector',[0 -1 0]);
   light('Parent', a2, 'Style', 'local');

Have a look here for an example. Its a quicktime movie. You can flip though it frame by frame with the cursor keys.

Thanks for any help!

http://www.uea.ac.uk/~tmg06qyu/plotflip.mov