Nope, DD bikes can enter F400,
Same as it was a few years ago with New Era where we use to enter the 400 Allcomers

Lol, but we got qually and 2 races for £25 back then!

Really, I thought you only got one race for the £25 and qually and two races for £60, back when track hire was cheaper and VAT was less, and the races were about half as long, before New Era folded and there wasn't talk of Mallory closing

Just found a New era Entry form for Mallory 2010

One 8 Lap Allcomers race is £25.
If an extra Class (Two 10 Lap Races plus Practice) is entered then that is an extra £60.

Based on that two extra races and qually at Oulton for £60 looks to be a fair price

will they be the moto solo allcomers- wouldn't that mean going straight from it into our race as they are next to each other in the schedule? is that even possible fitness aside?

Must be my hitting 40 that's ruined my memory!
Defo remember following a 12yr old Jake Byford round Castle Combe in qually and scrapping with a big bloke on a KTM in a couple of races. Could've been 1 race per day or could've been a year apart!

New Era did do a 3rd option (not usually on the entry form) where you could enter a second class and do only one of the races plus the qualifying. This was the preferred option for many and cost £30 iirc, brilliant I thought when the 400 qualily at Oulton was the session before DD qualiy, then I crashed in DD qualiy then arriving on my already warm tyres at the first chicane a lot faster than Mike Attack was on his cold tyres, braking hard when cranked over didn't work out to well for me