I have been thinking about switching to Beeman MFX arrows, and was wondering about other setups. I was thinking 400s. I'll be drawing 28" at about 57#. Anybody have a similar setup that may help me get close to the right size tip?

unfortunately, the only true way to know if a shaft/arrow will work best for your and your bow(s) is to test out diff'rent carbon spines.  get or borrow or make up a carbon spine test kit ... trust me on this, there really is no substitute if you want to be sure to have well flying arrows.

A 400 around 30" long with a brass insert should be close. You could also shoot a 500 with brass insert and shorten to around 29". Either one should fly well with some length adjustment.

A 400 with a 125 grain tip and the 75 grain insert left full length would be where I would start. Bareshaft tune and cut off the nock end till it is flying well.

Are you using a fast flight string material? I used them with a recurve tht pulled 48# cut to 29" with 150 up front and they were too stiff. I found 500 to be better but still not right and far too weak. Also, keep in mind the skinniness of the arrow brings it closer to center which stiffens the spine as well, if I had to guess, assuming you're using low stretch string materials, I would do what cyred4d suggests and have access to bump the front weight as well. If you can get 275 up front, it will put you into efoc and should greatly help penetration and accuracy. They are great arrows, but a little finicky.

Thank you all for your comments.

Im doing the same thing right now with the beeman 500's I have a 100 grain insert with 125 field points shooting a 29" arrow gets me really close.

I am shooting 56#. 31" 340, 75 grain insert, 150 heads. I have a little fine tuning to do, but so far, so good. Once the neck heals, I will continue to adjust point weight.
These arrows are tough! I think you will be happy with them.

Rob is right....but maybe we can get you in the ball park!!   :cool:  

I shoot a 60" recurve that is 56 @ 28". I shoot a skinny fast flight string.  I pull to 28 and a 1/2. My arrows are Beeman 400s cut to 29" excactly. I use the standard HIT insert (15 grains) and 250 grain point and get perfect arrow flight.

Great arrows! They are incredibly tough!

 

I shoot 54# and 56# at 27in with a 28in Beman 500 with 225grs of tip weight and they spine perfect, can also shoot the 400's but have to cut them at 30in with same tip weight.  A 400 shaft at your draw length with proper tip weight should work out just fine.