Henlow had 21 entries in the book when electing to delay closure of their 36 runner Super Sprint until Thursday.
Heats of the 277 metre event take place live on RPGTV on Sunday with semis and final to follow on consecutive Sundays. The winner collects £2,000.
Racing manager Paul Mellor said: “I was certain it would fill, but hopefully the extra day will make all the difference. We also have some places free in the 460m, 550m, and 692m opens.
