The DSL is not the amp to be trying to fit "big bottles" into.
As AmericanViking says, they will barely physically fit and will certainly lead over-heating problems.
jcmjmp, is also right. The current OT is not suitable and would need to upgraded, probably no a bad move for a DSL anyways
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By "bigger" do you mean that you want more low end?
KT77s do not have a good history with DSLs but why not try EL34Ls or EL34Bs?
What speakers are you using? Cab type?