Well, welcome but why did you decide to start with 5 as a first time bp owner? Ok, the girth of any bp at it's widest point is the rule also but some leeway is given and it's I think,1/8 to 1/4 inch. Enough for you to see a slight bulge. The 10-20% rule is also a guideline and there is room for adjustments. 20% of 250 is 50, 20% of 300 is 60. So, if you go with the heaviest bp at 300 grams you are well under the 20%. You mentioned the weanlings are about 38-45gms. You can go with something a bit larger for the heavier bps. Actually at those weights you are safely within the 20% rule. Remember that these are just guidelines. Stay in peace and not pieces.![]()