A little late to the party but I have the same issue and have a solution for it that worked, without changing the "Limited" partner box

Go to Schedule K, line 14A for Self Employment Earnings  Double click the number that takes you through to the "Net Self-Employment Earnings Worksheet".

One line 4d, you can type in a Special allocation code and an amount.  If you put that same Special Allocation code (like a "1") on the partner you want to have SE tax and a ratio %, it will allocate the amount you type on this form to his K1 as self-employment earnings.  The amount is usually the same as the amount of ordinary income on line 1