Angled notches

Hullo!

I’m making a couple of saw horses, loosely based on this design:

http://www.popularmechanics.com/home/how-to-plans/woodworking/4248458

I didn’t really look at the plans more than for just a cursory glance because I wanted to try doing something myself. I also didn’t look at the size of the stock either!

So I ended up with a slightly larger sized main board; 145×90 to be precise. I think now that’s too large, but what’s done is done and once they’re finished they’ll be fine.

I marked and cut all the rebates, angled towards each end to give stability, but my question comes with cutting the angles from top to bottom to give the legs their outwards splay for even more stability again.

What I chose to do was to mark the cut depth at the top smaller than the cut depth at the bottom, and started chiselling out the inside of the rebates.

Because of the depth of the board however, I’m having considerable difficulty making a smooth notch with a consistent angle without carving too deep or not deep enough.

I realise I could have cut the notch straight and instead cut angles off the legs. However I also chose slightly thinner legs than perhaps I should have; 45×19, so cutting angles on them felt like I would end up with not enough strength in the wood.

Regardless there’s got to be a right technique for doing what I’m trying to do, and I’d like to hear all your thoughts!

One thought I had was to use a rasp after carving the bulk of it out.

Any ideas as to the “right way” to go about doing these?

(I realise I probably haven’t described the situation well so I could add photos to explain further if necessary.

Thanks!