Are Stock Yield Enhancement Program loans made only in increments of 100?

There is no impact from lending stock through the Stock Yield Enhancement Program on the calculation of your margin and your excess liquidity. Your ability to borrow is still based on your stock positions…

No, unfortunately it is not possible to disable share lending with respect to the protection and hypothecation rules of the SEC or the Stock Yield Enhancement Program for an individual security. The only way to prevent a security from being lent is by owning all of your securities outright (no margin loan) and by not participating in the Stock Yield Enhancement Program. …

In the event that the demand for borrowing a given security is less than the supply of shares available to lend from participants in the Stock Yield Enhancement Program, loans will be allocated on a pro rata basis. 

Example…

In the event that the demand for borrowing a given security is less than the supply of shares available to lend from participants in our Stock Yield Enhancement Program, loans will be allocated on a pro rata basis (e.g. if aggregate supply is 20,000 and demand is 10,000, each client will be eligible to have 50% of his/her shares lent)…