I was wondering around what size i should build an outrigger with a 25cc homelite. I don't want to make it too big because it is just a stock homelite right now.

25cc Gas Class riggers generally have a tub length from @ 42" to @ 46"
pending on 3 or 4 point design, if sponson are equal too or further out in front than nose of tub.
LOTS of design criteria dictate the proportions of the bits and pieces making up the hull

That now said ... A homelite or any engine with a PTO side flywheel will be very difficult in getting it low enough and set with a shallow drive angle in a rigger tub. IMO using such an engine design is going to be troublesome.

Or just build your tub tall and base your design around that engine, if and when you change engines you will have likely learned enough that building another tub or rigger will be your next project

Thanks Scott
what are the pros and cons with the sponson infront or equal to the nose?

That alone does not matter, what does is where sponsons trailing edge is dictating the weight distribution on weight sponsons carry and tail end has on it.
Sponsons in general need to large enough to float the total boats weight, have contact surface enough to lift hull onto step etc ...
If sponson are not or can not be made wider to give the correct characteristics they must be built longer.
shape of engine area, sponson boom spacing all will alter the tubs proportions and that of the orientation of sponsons nose to tub nose.

** Are you building from plans or some known design platform or just winging it ?