Profit/Loss Allocation with SDIRA partnerships

Do profits/losses in a partnership of self-directed IRAs have to be based on the percentage of contribution?  For example, one party’s IRA contributes $90K, the other $10K for the purchase of a $100K property.  Can profits be split 50 – 50? Or do they have to be allocated 90 – 10? The parties are friends and not disqualified.