After putting on an 0320 engine on a standard nose long and not adding or removing the lead that was already in there, I got this reading from the scales (nose gear needs to be down---and the longerons need to be level---use wood blocks to prop up the nose wheel until level---make sure to zeroize the scale with the wood blocks on it):
--------net-----arm--------moment
Right--485-----110--------53350
Left----483-----110--------53130
nose---29------19.6-------568.4
ballast-neg30--40---------neg1200 (this is temporary weight next to inst panel to keep nose from flipping over)
total----967-----109.4-----105848.4
You should then cross check these with several weight figures (pilot + 36gal of fuel, normal single cruise (16 gal of fuel), normal cruise with my wife, max gross wt).
As an example of me (pilot + 36 gal of fuel)
-----------------wt---------station-------moment
empty A/C-----967--------109.4--------105848.4
fuel (36 gal)---219.6------104.5--------22948.2
pilot------------145---------59-----------8555
total-----------1331.6------103.15------137351.6
If you check the CG of 103.15 with the CG limits, you will see that I am beyond the aft limit by .15 inches (the aft limit is the more dangerous of the two).
Doing some quick math, I found that 9 more pounds in my short nose would do the trick---here is what you get:
Same example of me but with ballast (pilot with 36 gal of fuel)
-----------------wt------station-------moment
empty A/C-----967----109.4--------105848.4
fuel (36 gal)----219.6--104.5-------22948.2
pilot-------------145-----59----------8555
ballast-----------9-------5------------45
total-------------1340.6--102.48-----137396.6
102.48 puts me pretty far back in the envelope (97 is the forward limit---103 is the aft limit------99 to 101.5 is the is the first flight limit-------keep in mind that weight is another dimension of the envelope----but I won't discuss here).
Doing a quick check with my other sample configurations, I get the following:
Normal single cruise (by myself with 16 gallons): 101.5
Normal wife cruise (wife and 16 gallons) 101.2
Load up (wife, bags, 36 gal of fuel): 102.12 and 1520 lbs
This little exercise shows that for the conditions I have listed, I have a safe balance. The other thing you need to check from here is how much deviation off of my pilot weight can I tolerate and still be within balance limits----you will want to post this weight tolerance in the front cockpit.
If you use a spreadsheet like Excel, this goes pretty fast